Methods and systems for nondestructive material inspection

ABSTRACT

A method for determining one or more material conditions of a hysteretic ferromagnetic material and/or a nonhysteretic material can include interrogating the hysteretic ferromagnetic material and/or the nonhysteretic material with an input time varying magnetic field and detecting a magnetic response and/or acoustic response over time from the hysteretic ferromagnetic material and/or the nonhysteretic material. The method can also include determining a time dependent nonlinear characteristic of the received magnetic response and/or acoustic response and correlating the time dependent nonlinear characteristic of the received magnetic response or acoustic response to one or more material conditions of the material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/585,167 entitled “Methods And Systems For Nondestructive MaterialInspection” filed on Nov. 13, 2017, which is hereby incorporated byreference here in its entirety. This application is related to threeother co-pending U.S. provisional applications, filed on Nov. 13, 2017:U.S. Provisional Application No. 62/585,177 entitled “Methods AndSystems For Nondestructive Material Inspection”; U.S. ProvisionalApplication No. 62/585,185 entitled “Methods Of Using NondestructiveMaterial Inspection Systems”; and U.S. Provisional Application No.62/585,191 entitled “Methods Of Using Nondestructive Material InspectionSystems”, each of which are hereby incorporated by reference here in itsentirety.

FIELD

The present disclosure relates to material inspection, more specificallyto nondestructive material inspection.

BACKGROUND

Systems and methods to evaluate hard spots and/or other suitablematerial conditions and inhomogeneities (e.g., in pipeline steel orother suitable materials) for nondestructive inspection of pipeline,piping, steel plates, welded structures and welds of different typesthat can include, but are not limited to, girth welds, fillet welds, lapwelds and butt welds are valuable in determining material integrity(e.g., pipeline integrity) as well as material and weld quality. Suchsystems and methods for example, can obtain information on welds andpipeline materials nondestructively on such materials.

Currently, pipeline inspection gauges (PIGs) have been used as a tool toperform nondestructive pipeline inspection to detect anomalies anddefects in a pipe, such as cracks and hard spots. The most commonly usedtechnologies include magnetic flux leakage (MFL), ultrasonic crackdetection tool (UT), and electromagnetic acoustic transducer (EMAT) thatcouples electromagnetic energy with a mechanic wave. Similarly, weldsare non-destructively inspected using technologies including magneticparticle testing, ultrasonic testing, and eddy current testing. Allthese inspection technologies are based on the principle that theanomalies and defects possess some material properties that aredetectably different from that of the bulk material, e.g., the leakedmagnetic flux due to difference in magnetic permeabilities, or thereflected ultrasonics due to difference in mechanical vibrationbehaviors.

There is a useful but overlooked material property that can be used todetect anomalies and defects in pipeline, piping, steel plates, weldedstructures, and welds of different types that can include, but are notlimited to, girth welds, fillet welds, lap welds and butt welds. This isthe nonlinear nature of the magnetic response in ferromagneticmaterials. The nonlinear magnetic response provides information andaccuracy not attainable with the current methods which probe magneticflux leakage or linear response functions. Because of the importance ofmaterial integrity as well as material and weld quality, there is acontinuing need to further improve the art of nondestructive materialinspection by improving the inspection systems and methods. The presentdisclosure provides a solution for this need.

SUMMARY

In accordance with at least one aspect of this disclosure, a method fordetermining one or more material conditions of a sample composed of atleast one hysteretic ferromagnetic material and/or at least onenonhysteretic material. This method can include interrogating the samplewith an input time varying magnetic field and detecting the magneticresponses or acoustic responses over time from the hystereticferromagnetic materials and/or the nonhysteretic material. The methodcan also include determining a time dependent non-linear characteristicof the received magnetic field or acoustic responses and correlating thetime dependent nonlinear characteristic of the received magneticresponses or acoustic responses to one or more material conditions ofthe material.

Determining the time dependent non-linear characteristic can includeperforming a frequency domain analysis such as power spectral densityanalysis of the received magnetic field or acoustic responses to createpower spectral density data. In certain embodiments, determining thetime dependent non-linear characteristic can include determining one ormore harmonic peak values of the power spectral density (PSD) data.

Determining the one or more harmonic peak values can include determiningone or more harmonic coefficients of the spectral density data. Forexample, determining the one or more harmonic coefficients and/or peakvalues can include determining odd harmonic coefficients and/or peakvalues of the spectral density data.

In certain embodiments, determining the odd harmonic coefficients and/orpeak values can include determining 3rd and/or 5th harmonics of thespectral density data. Correlating the time dependent nonlinearcharacteristic can include comparing and correlating the 3rd and/or 5thharmonics to the one or more material conditions of the interrogatedsample.

The interrogated sample (comprising at least one hystereticferromagnetic material and/or at least one nonhysteretic material) caninclude, but is not limited to, a test material composed of at least onematerial phase with one or more material conditions. The one or morematerial conditions can include, but are not limited to, the presence ofat least one material phase of the hysteretic ferromagnetic materialand/or the nonhysteretic material. In certain embodiments, thehysteretic ferromagnetic material can include, but is not limited tosteel, nickel, cobalt, and their alloys, such as a variety of carbonsteels. In certain embodiments, the nonhysteretic material can include,but is not limited to air, aluminum, austenitic stainless steel, duplexstainless steel, and high manganese steel. The material phase caninclude, but is not limited to, at least one of austenite, martensite,ferrite, pearlite, bainite, lath bainite, acicular ferrite, andquasi-polygonal ferrite with different chemical compositions and/orcrystallographic orientations. The inhomogeneities of a sample caninclude, but are not limited to, a test material composed of more thanone material phase. Nonlimiting examples of inhomogeneities are hardspots and/or cracks/defects, e.g., in a steel pipe.

In accordance with at least one aspect of this disclosure, anon-transitory computer readable medium can include instructions forperforming any suitable method as described herein and/or any suitableportion(s) thereof. For example, the method can include generating atime varying magnetic field and detecting a magnetic response oracoustic response signal over time from a magnetic sensor or acousticsensor, determining a time dependent non-linear characteristic of thereceived magnetic field or acoustic responses, and correlating the timedependent nonlinear characteristic of the received magnetic response oracoustic responses to one or more material conditions of the material.Any other suitable portions of any embodiment of a method as describedherein can be included additionally or alternatively.

In accordance with at least one aspect of this disclosure, a device fordetecting one or more material conditions of an interrogated samplecomposed of at least one hysteretic ferromagnetic material and/or atleast one nonhysteretic material can include a magnetic transmitterconfigured to output an interrogation magnetic field; a magnetic sensoror an acoustic sensor configured to receive a magnetic response or anacoustic response, respectively; and to convert the magnetic response orthe acoustic response into magnetic signals or acoustic responsesignals, and a processor, configured to execute any suitable method asdescribed herein and/or any suitable portion(s) thereof. In certainembodiments, the device can include an indicator configured to indicateto a user the one or more conditions of the material. In certainembodiments, the output device can include an indicator, which impliesto notify one or more nearby users for appropriate immediate, real-timeactions, and the users can directly observe the indicator. In some otherembodiments, the output device 207 can also include, a device forcommunicating to users, which also implies notify users for appropriateimmediate, real-time actions, but the users may be at a remote location,and the communication may be through wired or wireless routes. In someother embodiments, the output device 207 can also include, a datacollection and storage device for later retrieval and post-processing,which is not for immediate, real-time actions.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,embodiments thereof will be described in detail herein below withreference to certain figures, wherein:

FIG. 1 is a flow diagram of an embodiment of a method in accordance withthis disclosure.

FIG. 2A is a schematic diagram of an embodiment of a device inaccordance with this disclosure, shown having a transmitting coil and apickup coil on the same side of a material.

FIGS. 2B-2D are power spectral density charts of the embodiment of FIG.2A in use on Air, Martensite, and Ferrite, respectively.

FIG. 3A is a schematic diagram of an embodiment of a device inaccordance with this disclosure, shown having a transmitting coil and apickup coil on the opposite side of a material.

FIGS. 3B-3D are power spectral density charts of the embodiment of FIG.3A in use on Air, Martensite, and Ferrite, respectively.

FIGS. 4A and 4B show simulation results on nonlinear magnetic detectionof model materials with a same side configuration (e.g., of FIG. 2A).

FIGS. 5A and 5B show schematic embodiments of a set up to test nonlinearmagnetic response of model materials under strong external magneticfield.

FIGS. 6A-6C show second harmonics PSD test results at differentfrequencies.

FIGS. 7A-7C show axial symmetric simulation of a horseshoe magnet on asteel pipe.

FIG. 8A shows an embodiment of a setup for nonlinear magnetoacousticdetection.

FIG. 8B shows PSD results for nonlinear magnetoacoustic detection.

FIG. 9 is an example arrangement that includes 4 copies of magneticsensors and/or acoustic sensors at different locations around and/orpaired with each magnetic transmitter.

FIG. 10 is an example arrangement that includes 8 copies of magneticsensors and/or acoustic sensors at different locations around and/orpaired with each magnetic transmitter.

FIGS. 11A-11F shows data of nonlinear magnetic detection on real pipewith hard phase in the weld (FIGS. 11A, 11B, 11D, and 11E) and pipesection without hard phase in the weld (FIGS. 11C and 11F).

FIGS. 12A-12C show embodiments of the detection and differentiationbetween nonhysteretic material and nonhysteretic material withinhomogeneities of hysteretic ferromagnetic materials.

FIGS. 13A-13E show an application of a device of the present disclosureto detect anomalies in real pipeline steel. FIGS. 13A and 13B are datamaps generated from two configurations of the device relative to thesample. FIG. 13C is a data map with combined data to sets from bothFIGS. 13A and 13B and at any specific location FIG. 13C only uses thelower value of the normalized 3^(rd) harmonics between FIGS. 13A and13B. FIG. 13E is an overlay of Vickers Hardness (VHN) measurements onthe sample photo. FIG. 13D is an excerpt of data from FIG. 13E.

FIGS. 14A-14C are power spectral density charts in use on Air,Martensite, and Ferrite, respectively.

FIGS. 15A-15B show an application of a device of the present disclosureto detect anomalies in carbon steel plate.

FIGS. 16A-16B show an application of a device of the present disclosureto detect anomalies in carbon steel plate.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claimsherein are modified by “about” or “approximately” the indicated value,and take into account experimental error and variations that would beexpected by a person having ordinary skill in the art. The currentinvention relates to methods and apparatus to detect nonlinear magneticresponse of a sample composed of at least one hysteretic ferromagneticmaterial. The linear response function of a magnetic material is givenby the equation

B(x)=μ₀(H(x)+M(x))=F(H(x))

where H(x) is the applied field magnetic field strength (units ofampere/meter) which can vary with position (x) in space, M(x) is themagnetization (units of ampere/meter) which depends on position (x) aswell as the initial magnetization state of the material, μ₀ is themagnetic permeability constant (unit of henry/meter), B(x) is themagnetic flux density (units of Tesla) which can vary with position (x)in space, and F(H(x)) is a function that depends linearly on H(x).Hereafter, B(x), H(x), M(x) and F(H(x)) are referred to as B, H, M andF(H) respectively, and/or B(t), H(t), M(t) and F(H(t)) if thecorresponding parameters are varying with time. This linear dependenceis the type of response seen in static magnetic fields. Currentinspection tools such as magnetic flux leakage (MFL), andelectromagnetic acoustic transducer (EMAT) tools are configured torespond to the function that depends primarily linearly on H. It shouldbe noted that for a ferromagnetic material this dependence can becomplicated. When the applied field is time varying, the linear operatorno longer describes the relationship between the applied magnetic fieldand the magnetization. The magnetic flux density B(t) in a ferromagneticmaterial with an applied time varying magnetic field H(t) can beapproximated by a linear operator along with a time integral of a seriesof nonlinear functions:

$\begin{matrix}\begin{matrix}{{B(t)} = {{F\left( {H(t)} \right)} + {\int_{- \infty}^{0}{{F_{1}\left( {H\left( {t + \tau} \right)} \right)}d\; \tau}} +}} \\{{{\int_{- \infty}^{0}{{F_{2}\left( {H^{2}\left( {t + \tau} \right)} \right)}d\; \tau}} +}} \\{{{\int_{- \infty}^{0}{{F_{3}\left( {H^{3}\left( {t + \tau} \right)} \right)}d\; \tau}} + \ldots}} \\{= {{F\left( {H(t)} \right)} + {\int_{- \infty}^{0}{\sum\limits_{n = 1}^{\infty}{{F_{n}\left( {H^{n}\left( {t + \tau} \right)} \right)}d\; \tau}}}}}\end{matrix} & {{Equation}\mspace{14mu} 1}\end{matrix}$

The function F₂ gives rise to a second order nonlinear response, thefunction F₃ gives rise to a third order nonlinear response, and thefunction F_(n) gives rise to an nth order nonlinear response. The timeintegral ∫_(−∞) ⁰F_(n)(H^(n)(t+τ))dτ represents that the magnetic fluxdensity B(t) depends on the history of function F_(n)(H^(n)(t)).

The present invention utilizes these nonlinear responses to provide abetter way to characterize material conditions and inhomogeneities inferromagnetic materials. If the applied field H(t) is sinusoidal andvaries sinusoidally with a frequency ω, then the second order responsevaries as 2ω, the third order response varies as 3ω and the nth orderresponse varies as nω. If the applied field has an arbitrary timedependence then the nonlinear response can be extracted from an analysisof the time dependence of signals that can arise from magnetization andthe magnetic flux density (B(t) in Eq.1). In some cases this can be doneby Fourier analysis of the time dependence of signals arising frommagnetization and the magnetic flux density (B(t) in Eq.1). In someinstances the nonlinear response can be directly characterized from thetime dependence of signals arising from magnetization and the magneticflux density (B(t) in Eq.1).

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, an illustrative view of an embodiment of a method inaccordance with the disclosure is shown in FIG. 1 and the method isdesignated generally by reference character 100. Other embodimentsand/or aspects of this disclosure are shown in FIGS. 2A-16B. The systemsand methods described herein can be used to determine materialconditions of a material (e.g., a material phase and/or imperfection ina metal pipeline).

Below a general understanding of the nonlinear magnetic response inhysteretic ferromagnetic materials is provided. Embodiments describedbelow provide a fast, simple, and general way to detect materialconditions and inhomogeneities of a sample being studied. Nonlimitingexamples of inhomogeneities are hard spots and/or cracks/defects, e.g.,in a steel pipe. Certain embodiments described herein do not require abuilt-in ferromagnetic core, and can thus be calibrated in airenvironment to provide precise background signal. The method also allowscalibration in environments other than air (for example samples immersedin oil).

The nonlinear response of the magnetic flux density (B(t) in Eq.1) in anapplied time varying magnetic field gives rise to a number of responsesthat can be detected. These responses track the time dependence of themagnetic flux density created from the applied time varying magneticfield and the nonlinear responses arise from the hysteretic responses ofthe magnetization and the magnetic flux density (B(t) in Eq.1). Boththeoretically and experimentally, it is shown that symmetric hystereticresponses leads to odd numbers of harmonics, while asymmetric hystereticresponses lead to even numbers of harmonics. A symmetric hysteresisresponse usually connects to, but not limited to, ferromagneticmaterials, and an asymmetric hysteresis response usually connects to,but not limited to, the residual magnetization state in the hystereticmaterials, embodiments can also be applied to detect magnetization stateof hysteretic materials. One embodiment of the present inventionincludes interrogation of a sample with a time varying magnetic fieldfrom a magnetic transmitter and detection of the magnetic flux density(B(t) in Eq.1) with a magnetic sensor that is in proximity to thesample. A variation of this embodiment includes the incorporation of aDC magnetic field that biases the magnetization. Another variationincludes the measurement of a sample with a residual magnetization. Yetanother variation includes measurement of a sample that has beendegaussed. A different embodiment includes interrogation of a samplewith a time varying magnetic field from a magnetic transmitter anddetection of the magnetic flux density (B(t) in Eq.1) and a nonlinearmagneto-acoustic response (e.g., similar to EMAT), but looks at thenonlinear spectra of acoustic signal. A variation of this embodimentincludes the incorporation of a DC magnetic field that biases themagnetization. Another variation includes the measurement of a samplewith a residual magnetization. Yet another variation includesmeasurement of a sample that has been degaussed.

The general principle of the nonlinear magnetic response relies onapplying a time varying magnetic field H(t) to a sample and detecting aresponse. This principle will be illustrated from the case in which thetime varying magnetic field is an AC magnetic modulation H_(AC)({rightarrow over (r)}, t)=H₁({right arrow over (r)})e^(iωt) with a spatiallyvaring magnetizing field H₁({right arrow over (r)}) and angularfrequency ω=2πf. Such AC modulation can be achieved by a time varyingelectrical current J_(f)=J₀({right arrow over (r)})e^(iωt) (consideringAmpere's law

${{\nabla{\times H_{1}}} = {J_{f} + \frac{\partial D}{\partial t}}},$

and the second term

$\frac{\partial D}{\partial t}$

is negligible in our frequency range

$\left. {{\frac{\partial D}{\partial t}} \sim {{{- i}\; {\omega\epsilon}\; E}}{\sigma {E}}} \right).$

A DC magnetizing field H_(DC)({right arrow over (r)}) can also beapplied by a DC electrical current or permanent magnet, and leads to atotal field generated by the source: H_(s)({right arrow over (r)},t)=H_(DC)({right arrow over (r)})+H_(AC)({right arrow over (r)})e^(iωt).For ferromagnetic materials such as carbon steel and other ferriticphase in steels, the relative permeability μ_(r) that connects field Band H is a hysteretic and nonlinear operator. Therefore the primarymagnetic field B_(s)({right arrow over (r)}, t)=μ₀μ_(r) H_(s)({rightarrow over (r)}, t) would be nonlinear inside the ferromagneticmaterials and can be described as Taylor series

$\begin{matrix}{{B_{s}\left( {\overset{\rightarrow}{r},t} \right)} = {\sum\limits_{n = {- \infty}}^{n = \infty}{{B_{n}\left( \overset{\rightarrow}{r} \right)}e^{i\; n\; \omega \; t}}}} & {{Equation}\mspace{14mu} (2)}\end{matrix}$

With Faraday's law

${{\nabla{\times {E_{2}\left( {\overset{\rightarrow}{r},t} \right)}}} = {- \frac{\partial{B_{s}\left( {\overset{\rightarrow}{r},t} \right)}}{\partial t}}},$

the induced electric field in steel E₂({right arrow over (r)}, t) andthe resulting Eddy current J_(eddy)({right arrow over (r)},t)=σE₂({right arrow over (r)}, t) are both nonlinear, as theconductivity σ in steel is normally a scalar and linear operator. TheEddy current is only distributed around the surface of conductivematerials with a skin depth

${d_{p} = \sqrt{\frac{1}{\pi \; f\; \mu \; \sigma}}},$

and it generates a secondary magnetizing field H₂({right arrow over(r)}, t) from Ampere's law ∇×H₂J_(eddy)=σE₂. As a result, the secondarymagnetizing field

${H_{2}} \propto {{- \sigma}\frac{\partial B_{s}}{\partial t}}$

would contain similar nonlinear information as the primary fieldB_(s)({right arrow over (r)}, t).

Different ferromagnetic materials have different hysteresis curves andmagnetic responses, and would result in different nonlinear harmoniccoefficient B_(n)({right arrow over (r)}) under the same magneticmodulation. The difference in the harmonic coefficients can be measuredwith two methods:

1. Nonlinear magnetic detection: The total magnetizing field isnonlinear, and can be measured by a magnetic sensor at a point A in air:H_(total)({right arrow over (r_(A))}, t)=H_(DC)({right arrow over(r_(A))})+H_(AC)({right arrow over (r_(A))})e^(iωt)+H₂({right arrow over(r_(A))}, t).

2. Nonlinear magnetoacoustic detection. With a large constant DCmagnetic field B_(DC)({right arrow over (r)}), a strong Lorentz bodyforce f({right arrow over (r)}, t)=J_(eddy)({right arrow over (r)},t)×B_(DC)({right arrow over (r)}) takes place and launches atime-varying mechanic wave. Such magnetoacoustic response is alsononlinear.

Finally considered is the generation of different nonlinear harmonicsunder sinusoidal modulation J_(f)=J₀ ({right arrow over (r)})e^(iωt),and in this case all the nonlinear effects originate from B_(s)({rightarrow over (r)}, t)=μ₀μ_(r) H_(s)({right arrow over (r)}, t). When thelocal hysteresis B-H loop is symmetric inside the hysteretic materials,B_(s)({right arrow over (r)}, t) reverse its direction after half aperiod B_(s)({right arrow over (r)}, t)=−B_(s)({right arrow over (r)},t+T/2). This normally happens at near zero magnetization. With Taylorexpansion from equation (1), the symmetry constraint suggests Σ_(n=−∞)^(n=∞)B_(n)({right arrow over (r)})e^(inωt)=−Σ_(n=−∞) ^(n=∞)B_(n)({rightarrow over (r)})e^(inω(t+T/)2) and B_(n)({right arrow over(r)})=(−1)^((n+1))B_(n)({right arrow over (r)}). Therefore for evennumbers of n, the harmonic coefficient B_(n)({right arrow over (r)})=0.In other words, a symmetric B-H curve prohibits the generation of evennumber of harmonics and only allows odd number of harmonics. Incontrast, if the B-H loop is asymmetric, B_(s)({right arrow over (r)},t)≠−B_(s)({right arrow over (r)}, t+T/2) and all Taylor coefficientB_(n)({right arrow over (r)}) in the expansion could exist. In otherwords, an asymmetric B-H curve allows for both odd and even numbers ofharmonics.

Referring now to FIG. 1 a method 100 for determining one or morematerial conditions of a sample composed of at least one hystereticferromagnetic material can include interrogating (e.g., at block 101)the hysteretic ferromagnetic material by applying a time varyingmagnetic field. Optionally in block 101 an additional DC magnetic fieldcan be applied. Optionally a degaussing magnetic field can be applied inblock 101. Optionally the sample in block 101 can have a residualmagnetization. A DC magnetic field is a magnetic field that is notvarying over time, and a degaussing magnetic field is a time-varyingmagnetic field that is used to eliminate residual magnetization of amaterial. The time varying magnetic response or acoustic response isdetected in block 103. The method 100 can also include determining(e.g., at block 105) a time dependent non-linear characteristic of thereceived magnetic field or acoustic response and correlating (e.g., atblock 107) the time dependent nonlinear characteristic of the receivedmagnetic response or acoustic response to one or more materialconditions of the material.

Interrogating the hysteretic ferromagnetic material with an input timevarying magnetic field can include, but is not limited to, utilizing atleast one magnetic transmitter that generates a time varying magneticfield and placing the magnetic transmitter at a nearby location to theinterrogated sample. For example, an example proximity (or nearbylocation) for the magnetic transmitter is 1 cm to the surface of theinterrogated sample; a more preferred nearby location for the magnetictransmitter is 0.2 cm or less to the surface of the interrogated sample;an even more preferred nearby location for the magnetic transmitter isin direct contact on the surface of the interrogated sample.

The time varying magnetic field can include, but is not limited to, acombination of sinusoidal wave, square wave, triangular wave andsymmetric and asymmetric pulses. In certain embodiments, a preferredtime varying magnetic field can include sinusoidal wave with peakamplitude ranging from 0.01 milliTesla to 1 Tesla, and frequency rangingfrom 1 Hz to 1 MHz. A more preferred time varying magnetic field caninclude sinusoidal wave with peak amplitudes from 0.1 milliTesla to 10milliTesla, and frequency ranging from 100 Hz to 100 kHz. For examining4140 carbon steel materials, and other carbon steel materials made withthe Thermo-Mechanical Controlled Processing (TMCP) such as X60 and/orX65 carbon steel, a preferred time varying magnetic field can includesinusoidal wave with peak amplitude ranging from 0.01 milliTesla to 1Tesla, and frequency ranging from 1 Hz to 1 MHz; a more preferred timevarying magnetic field can include sinusoidal wave with peak amplitudesfrom 0.1 milliTesla to 10 milliTesla, and frequency ranging from 100 Hzto 100 kHz; an even more preferred time varying magnetic field caninclude sinusoidal wave with peak amplitudes from 0.1 milliTesla to 10milliTesla, and frequency ranging from 8 kHz to 100 kHz; an even morepreferred time varying magnetic field can include sinusoidal wave withpeak amplitudes from 0.5 milliTesla to 5 milliTesla, and frequencyranging from 8 kHz to 100 kHz.

Similar to the common practice in other non-destructive inspection tool,one familiar with the technique can optimize the time varying magneticfield by calibrating the nonlinear magnetic response and/or the size of3^(rd) harmonics with respect to frequency range, amplitude range, andmaterial phases.

The magnetic transmitter can include, but is not limited to, a device togenerate the time varying magnetic field, such as a transmitting coil, atranslating/rotating magnet such as Neodymium magnet, ceramic magnet,electromagnet or a superconducting magnet. In certain embodiments, apreferred magnetic transmitter can include a transmitting coil with anouter diameter between 2 mm to 10 cm, number of turns between 1 to100,000 and an inductance between 0.001 mH to 1000 mH. In certainembodiments, a more preferred magnetic transmitter can include atransmitting coil with an outer diameter between 5 mm to 5 cm, number ofturns between 10 to 1000 and an inductance between 0.01 mH to 100 mH. Incertain embodiments, an even more preferred magnetic transmitter caninclude a transmitting coil with an outer diameter of 1 inch (25.4 mm),100 turns, and an inductance of L˜0.25 mH. In certain embodiments, asmaller-diameter magnetic transmitter can be used to generate inspectionresults with higher lateral spatial resolution. In certain embodiments,an even more preferred magnetic transmitter can include one or morecoils with their diameters smaller than 1-inch to improve the lateralspatial resolution of the inspection results.

Detecting a magnetic response or an acoustic response can include, butis not limited to, utilizing at least one magnetic sensor or acousticsensor configured to receive a magnetic response or acoustic response,respectively, and to convert the magnetic response or acoustic responseinto magnetic response signals or acoustic response signals. Preferably,the magnetic sensor is located in a region near the magnetictransmitter. In one embodiment, the distance between the magnetic sensorand the magnetic transmitter is less than 50 meters, preferably lessthan 10 meters, preferably less than 1 meter, preferably less than 10centimeters, preferably less than 1 centimeter, preferably less than 1millimeter, and even more preferably in direct contact to each other.

A magnetic response can include, but is not limited to, a spatiallyvarying magnetic field produced by the interrogated material as a resultof input time varying magnetic field and any additional magnetic fields.A magnetic sensor can include, but is not limited to, a device toreceive the magnetic response from at least one point or averaged over asensing area, and convert the magnetic response to a digital or analogsignal that can be interpreted by a computer or observer, such as pickupcoils, Hall sensors, Fluxgate magnetometers, Cesium atomic magnetometersor superconducting SQUID magnetometers. In certain embodiments, apreferred magnetic sensor can include a sensing coil with an outerdiameter between 2 mm to 10 cm, number of turns between 1 to 100,000 andan inductance between 0.001 mH to 1000 mH. In certain embodiments, amore preferred magnetic transmitter can include a transmitting coil withan outer diameter between 5 mm to 5 cm, number of turns between 10 to1000 and an inductance between 0.01 mH to 100 mH. In certainembodiments, an even more preferred magnetic sensor can include asensing coil with an outer diameter of 1 inch, 100 turns, and aninductance of L˜0.25 mH. In certain embodiments, a smaller-diametermagnetic sensor can be used to generate inspection results with higherlateral spatial resolution. In certain embodiments, a more preferredmagnetic sensor can include one or more coils with their diameterssmaller than 1-inch to improve the lateral spatial resolution of theinspection results. In one embodiment, the magnetic sensor is chosen sothat it can respond sufficiently fast to record at least the signalarising from the second order nonlinear effect, in a more preferredembodiment the magnetic sensor is chosen so that it can respondsufficiently fast to record at least the signal arising from the thirdorder nonlinear effect, and in an even more preferred embodiment themagnetic sensor is chosen so that it can respond sufficiently fast torecord at least the signal arising from the fifth order nonlineareffect.

An acoustic response can include, but is not limited to, a mechanicalmotion produced by the interrogated material as a result of input timevarying magnetic field and any additional magnetic fields. An acousticsensor can include, but is not limited to, a device to receive theacoustic response from at least one point or averaged over a sensingarea, and convert the acoustic response to a digital or analogue signalthat can be interpreted by a computer or observer, such as piezoelectricacoustic transducer, microphone, seismometer, or geophone. In certainembodiments, a preferred acoustic sensor can include a ceramicpiezoelectric acoustic transducer with a diameter of 1.2 cm and aresonance frequency of 500 kHz. In one embodiment, the acoustic sensoris chosen so that it can respond sufficiently fast to record at leastthe signal arising from the second order nonlinear effect, in a morepreferred embodiment the acoustic sensor is chosen so that it canrespond sufficiently fast to record at least the signal arising from thethird order nonlinear effect and in an even more preferred embodimentthe sensor is chosen so that it can respond sufficiently fast to recordat least the signal arising from the fifth order nonlinear effect.

Determining the time dependent non-linear characteristic can includeperforming a frequency domain analysis such as power spectral densityanalysis of the received magnetic response or acoustic response tocreate power spectral density data. In certain embodiments, determiningthe time dependent non-linear characteristic can include determining oneor more harmonic peak values of the power spectral density data.

Determining the one or more harmonic peak values can include determiningone or more harmonic coefficients of the spectral density data. Forexample, determining the one or more harmonic coefficients and/or peakvalues can include determining odd harmonic coefficients and/or peakvalues of the spectral density data.

In certain embodiments, determining the odd harmonic coefficients and/orpeak values can include determining 3rd and/or 5th harmonics of thespectral density data. Correlating the time dependent nonlinearcharacteristic can include comparing and correlating the 3rd and/or 5thharmonics to the one or more material conditions of an interrogatedsample. In certain embodiments, a large 3rd harmonics of the spectraldensity data, ranging from 10⁻⁶ or above after normalization, correlateto a material condition that include, but is not limited to, thepresence of ferrite or pearlite carbon steel phases in an interrogatedsample; a small 3rd harmonics of the spectral density data, ranging from10⁻⁸ to 10⁻⁶ after normalization, correlate to a material condition thatinclude, but is not limited to, the presence of hard steel phase such asmartensite or lath bainite carbon steel phases, or nonhystereticmaterial such as air gap in an interrogated sample.

The interrogated sample can include, but is not limited to, a testmaterial composed of at least one material phases with one or morematerial conditions. The one or more material conditions can include,but are not limited to, at least one material phase of the hystereticferromagnetic material or the nonhysteretic material. In certainembodiments, the hysteretic ferromagnetic material can include, but isnot limited to steel, nickel, cobalt, and some of their alloys, such asa variety of carbon steels. In certain embodiments. The nonhystereticmaterial can include, but is not limited to air, aluminum, austeniticstainless steel, duplex stainless steel and high manganese steel. Thematerial phase can include, but is not limited to, at least one ofaustenite, martensite, ferrite, pearlite, bainite, lath bainite,acicular ferrite, and quasi-polygonal ferrite with different chemicalcompositions and/or crystallographic orientations. The inhomogeneitiesof a sample can include, but are not limited to, a test materialcomposed of more than one material phases. Nonlimiting examples ofinhomogeneities are hard spots and/or cracks/defects, e.g., in a steelpipe.

In accordance with at least one aspect of this disclosure, anon-transitory computer readable medium can include instructions forperforming any suitable method as described herein and/or any suitableportion(s) thereof. For example, the method can include generating atime varying magnetic field and detecting a magnetic response oracoustic response signal over time from a pickup coil, determining atime dependent non-linear characteristic of the received magnetic fieldor acoustic response, and correlating the time dependent nonlinearcharacteristic of the received magnetic response or acoustic response toone or more material conditions of the material. Any other suitableportions of any embodiment of a method as described herein can beincluded additionally or alternatively.

Referring additionally to FIG. 2A, in accordance with at least oneaspect of this disclosure, a device 200 for detecting one or morematerial conditions of a hysteretic ferromagnetic material (e.g., asample 221 comprising a hysteretic ferromagnetic material) can include atransmitting coil 201 configured to output an interrogation magneticfield, a pickup coil 203 or acoustic transducer (e.g., as described inmore detail below) configured to receive a magnetic response or acousticresponse, respectively, and to convert the magnetic response or acousticresponse into magnetic signals or acoustic response signals. The device200 can include a processor 205 configured to execute any suitablemethod, e.g., as described hereinabove and/or any suitable portion(s)thereof.

In certain embodiments, the device 200 can include an output device 207configured to indicate to a user the one or more conditions of thematerial. The system 200 can include any other suitable signalprocessing components (e.g., one or more digitizers, a current meter, asignal generator, one or more bandpass filters, one or morepre-amplifiers or amplifiers, etc.) as appreciated by those havingordinary skill in the art. The output device 207 can include, but is notlimited to, an indicator, which implies to notify one or more nearbyusers for appropriate immediate, real-time actions, and the users candirectly observe the indicator. The output device 207 can also include,but is not limited to, a device for communicating to users, which alsoimplies notify users for appropriate immediate, real-time actions, butthe users may be at a remote location, and the communication may throughwired or wireless routes. The output device 207 can also include, a datacollection and storage device for later retrieval and post-processingand analysis.

Carbon steels are key materials in the pipeline and oil & gas industry.Generally, all the carbon steels compose of multiple material phases.Ferrite (soft phase of carbon steel) is a key material phase in thecarbon steels. Hard phase, such as martensite or lath bainite could formin the steels when they have been rapidly quenched from high temperature(for example, from 900° C.) to room temperature, which could happenduring steel mill plate manufacture or an electric resistance seamwelding process. The presence of hard steel phase such as martensite orlath bainite phases can be particularly precarious as it is moresusceptible to failures and cracking compared to soft ferrite phase. Asa result, a carbon steel sample composed of ferrite and martensite aretested herein, since the application to pipelines is a good example ofwhere such devices can be used. Any other suitable materials andapplications are contemplated herein.

In the embodiment shown, a voltage or current signal can be generatedthrough the signal generator 209 (e.g., a sinusoidal wave of frequencyf). With current passing through, the transmitting coil 201 is used as amagnetic transmitter to generate a modulating magnetic field. Thetransmitting coil 201 used to produce data below includes an outerdiameter of about 1 inch, 100 turns, and an inductance of L˜0.25 mH. Theelectrical impedance of a transmitting coil isZ_(coil)=R_(internal)+iωL. Typically the internal resistanceR_(internal) of a coil is relatively small (<1Ω for the coil we tested),while the imaginary inductive term increases proportionally withfrequency. Any other suitable coil with any suitable characteristics canbe used.

To minimize the impedance effect of the inductor and maximize the outputcurrent, a capacitor C 211 is used to change the total impedance to

${Z_{coil} = {R_{internal} + {i\; \omega \; L} + \frac{1}{i\; \omega \; C}}},$

while imaginary term can be cancelled out when

${{i\; \omega \; L} + \frac{1}{i\; \omega \; C}} = {{0\mspace{14mu} {or}\mspace{14mu} C} = {\frac{1}{\omega^{2}L}.}}$

Frequencies from 1 kHz to 100 kHz were used in generating the databelow, and different capacitances can be used at different frequenciesto ensure that

$C \sim \frac{1}{\omega^{2}L}$

for me same transmitting coil 201. The current passing through thetransmitting coil 201 can be measured with a current meter 213 andrecorded with a first digitizer 215.

To detect the magnetic response from nearby materials, a magnetic sensorsuch as the pickup coil 203 can be used to measure time varying magneticsignal. The voltage generated through the pickup coil 203 is

${ɛ = {{- N}{\frac{d\; B}{dt} \cdot A}}},$

which is related to number of turns N of the pickup coil 203, timederivative of local magnetic field

$\frac{d\; B}{dt}$

and crosssection area of the loop A. This voltage can be measuredthrough a second digitizer 217, for example. An optional pre-amplifierand/or bandpass filter 219 can be utilized between pickup coil 203 andthe second digitizer 217, e.g., to enhance weak signal or detectspecific frequency components in the measured signal if necessary. Afterreceiving the waveforms of the transmitting current and pickup voltagefrom both digitizers, PSD analysis can be performed by the processor 205in real time to extract nonlinear coefficients and/or peak values of thetesting materials.

The transmitting coil 201, pickup coil 203, and the interrogatedmaterial can be arranged in any suitable configuration. Two specificexamples are shown in FIGS. 2A and 3A. In FIG. 2A, the transmitting coil201 and pickup coil 203 are placed to the same side of the interrogatedmaterial (e.g., ferromagnetic plate), and this configuration could bereadily applied to conventional PIG for nondestructive pipelineinspection. In FIG. 3A, an alternate configuration is shown with thetransmitting coil 201 and pickup coil 203 placed on opposite sides ofinterrogated material.

Accordingly, as shown in FIG. 2A, the system 200 can be configured foruse on a single side of the interrogated material. As presented above,in certain embodiments, the one or more conditions of the material to bedetermined can include a material phase, for example. Example resultsfor determining material phases for Air (as a baseline), Martensite (asa first phase), and Ferrite (as a second phase) in the place of thesample 221 are shown in the below Table 1 and in FIGS. 2B-2D.

As a control experiment, the device 200 was tested at 10 kHz frequencyin air without any conducting/magnetic materials within half a meter.The power spectral densities (PSDs) of transmitting current and pickupvoltage are shown as solid and dashed curves. The peaks of higher orderharmonics (2nd, 3rd, 4th, and 5th, etc.) are at least 7 orders ofmagnitude lower than the primary frequency of 10 kHz. These small valuesof harmonics are due to electronic processing and system noise, andshould be calibrated as a baseline for material testing.

TABLE 1 Harmonics normalized to 1^(st) peak 2^(nd) 3^(rd) 4^(th) 5^(th)Harmonics Harmonics Harmonics Harmonics Air (a) 4.71 × 10⁻⁸ 1.32 × 10⁻⁸3.92 × 10⁻⁹ 2.91 × 10⁻⁹ Martensite (b) 2.35 × 10⁻⁸ 4.58 × 10⁻⁷ 4.30 ×10⁻⁹ 2.43 × 10⁻⁸ Ferrite (c) 1.38 × 10⁻⁷ 3.60 × 10⁻⁵ 2.99 × 10⁻⁸ 1.07 ×10⁻⁶

Referring to FIG. 3A, in certain embodiments, the system 200 can beconfigured for use on opposite sides of the interrogated material.Example results for determining material phases for Air (as a baseline),Martensite (as a first phase), and Ferrite (as a second phase) are shownin the below Table 2 and in FIGS. 3B-3D.

TABLE 2 Harmonics normalized to 1^(st) peak 2^(nd) 3^(rd) 4^(th) 5^(th)Harmonics Harmonics Harmonics Harmonics Air (a) 4.72 × 10⁻⁸ 1.52 × 10⁻⁸4.22 × 10⁻⁹ 3.40 × 10⁻⁹ Martensite (b) 3.93 × 10⁻⁸ 2.01 × 10⁻⁷ 1.93 ×10⁻⁹ 2.14 × 10⁻⁸ Ferrite (c) 9.59 × 10⁻⁸ 1.17 × 10⁻⁵ 3.10 × 10⁻⁹ 3.44 ×10⁻⁶

As can be seen in both examples, odd harmonics show orders of magnitudedifferences between the different material types, allowing foridentification of different materials, for example. The nonlinearresponse changes dramatically once a coupon (sample 221) of martensiteor ferrite (e.g., 38.1 mm (L)×25.4 mm(W)×4.7 mm (H)) is placed at theend of the coils. The even numbers of harmonics do not experiencesignificant changes, while the peaks for odd number of harmonicsincrease dramatically, with the most significant increases coming from3rd and 5th harmonics at 30 kHz and 50 kHz (e.g., in FIGS. 2C and 2D).In particular, the peak of 3rd harmonics increases by over one order ofmagnitude with a martensite coupon (FIG. 2C) and over three orders ofmagnitude with ferrite coupon (FIG. 2D). In the data shown, the primaryharmonic peak is used as a standard calibration and normalized allhigher order harmonics coefficients with respect to the primary peak.

Again, the most distinguishing signatures were seen to be the 3rd and5th harmonics. The same phenomenon is observed with either the same-sideconfiguration (e.g., of FIG. 2A) or the opposite-side configuration(e.g., of FIG. 3A). In both configurations, the significant contrasts of3rd harmonics across air (˜1-×10⁻⁸), martensite (˜1×10⁻⁷ to 5×10⁻⁷) andferrite (˜1×10⁻⁵ to 5×1⁻⁵) provide unique nonlinear magnetic signaturesthat can be directly utilized to detect the hard phases such asmartensite phase that make up the hard spots in pipeline steel, forexample.

In principle, the self-inductance of the transmitting coil is changedwith ferromagnetic materials nearby, and the change should be naturallynonlinear due to the hysteretic response. We have observed relativelysmall increases in the PSDs of the transmitting current (solid curves inFIGS. 2B-3D) across air, martensite and ferrite samples. While it ispossible to differentiate ferromagnetic materials by just analyzingvoltage and current from a single transmitting coil, the signatures ofdifferent materials are not as distinguishable as compared to themeasured responses from pickup coil. In this regard, the transmittingcoil and the pickup coil can be the same coil in certain embodiments.

Referring to Table 3, in certain embodiments, the system 200 can beconfigured for use on a single side of the interrogated material and thetransmitting and pickup coils can be placed at a preferred nearbylocation with a limited distance to the surface of the interrogatedsample. The distance and/or the spacing between the interrogated sampleand the two coils is called a lift-off distance. While the Table 1 andFIGS. 2C-2D demonstrated unique nonlinear magnetic signatures when thetwo coils are in direct contact with the surface of the interrogatedsample, here Table 3 shows that similar unique nonlinear magneticsignatures are observed even when there is a lift-off distance of 0.8 mmor 2.0 mm. For either ferrite or martensite, the normalized 3^(rd)harmonics slightly decrease with increasing amount of lift-off distance,but overall the peak of 3rd harmonics in the case of ferrite is largerby about two orders of magnitude as compared to the case of martensite,regardless of the 0, 0.8 mm or 2.0 mm lift-off distance. This robust andsignificant contrasts of 3rd harmonics, martensite (˜1×10⁻⁷ to 5×10⁻⁷)and ferrite (˜1×10⁻⁵ to 5×10⁻⁵), provide unique nonlinear magneticsignatures that can be directly utilized to detect specific materialphases such as martensite phase even when a constant or time-varyinglift-off distance is present during applications.

TABLE 3 3^(rd) Harmonics normalized to 1^(st) peak No lift-off 0.8 mmlift-off 2.0 mm lift-off Martensite 4.6 × 10⁻⁷ 3.0 × 10⁻⁷ 1.3 × 10⁻⁷Ferrite 3.8 × 10⁻⁵ 2.8 × 10⁻⁵ 1.6 × 10⁻⁵

Referring to FIGS. 4A and 4B, computer simulations were performed toincorporate the magnetic hysteresis response and understand theexperimentally observed 3rd harmonics of ferrite and martensite phases.The hysteresis models used here were originally developed by Jiles andAtherton, and are known as J-A model. There are five parameters in J-Amodel to describe the hysteretic response of a specific material, and insimulations these five parameters are obtained by best matching J-Ahysteresis curves to experimental measurements in the literature. Forferrite and martensite phases, two different sets of parameters areobtained and the full hysteresis curves are shown in FIG. 4A (solidcurve for ferrite phase and dashed curve for martensite phase). Then aCOMSOL multiphysics computer software package is used to simulatemagnetic response under the same experimental condition and parametersas in FIGS. 2A-3D.

The simulation incorporates full Maxwell equation solver with five J-Aparameters to account for the nonlinear hysteretic magneticpermeability. As the simulation starts with zero residual magnetization,the results (FIG. 4B) show the presence of odd-number harmonics only inboth ferrite and martensite cases, which is consistent with thetheoretical description of symmetric B-H curve. Furthermore in thesimulation results, the 3rd and 5th harmonics of ferrite are about 1.5orders of magnitude (˜40 times) larger than those of martensite, whichalso agree with the experimental observations above. With the reliablesimulation tool, the quantitative linkage between the generation ofharmonics and hysteresis curve has been elucidated, and additionally itis possible to design specific amplitude and frequency of AC magneticmodulation to optimize the detection of hard phase in specificapplications.

FIG. 4A shows full hysteresis curves for ferrite (solid) and martensite(dashed). Five J-A parameters are obtained by matching hysteresis curvesto experimental measurements in literature. FIG. 4B shows simulatedPower Spectral Density (PSD) results for nonlinear magnetic detection ofmartensite (dashed) and ferrite (solid) in the configuration of FIG. 2A.As can be seen, only odd harmonics show up due to symmetricmagnetization. For 3rd and 5th harmonics, about 1.5 orders of magnitudedifference between ferrite and martensite is consistent withexperimental observations above.

In the next example, additional experimental tests are performed tobetter understand the measured non-linear signatures. As the hysteresisloop for ferromagnetic materials is highly nonlinear and historydependent, we would expect that the nonlinear magnetic response of thesematerials depend on their magnetization states. Therefore, themeasurement of nonlinear magnetic response could in principle be anindicator of magnetization state of the testing materials, and couldprovide additional information in the detection of magnetic anomalies.

Based on the theoretical description, a locally symmetric hysteresisloop would result in odd numbers of harmonics only and this would occurin two scenarios: 1) The material has small residual magnetizationcompared to its saturation magnetization, and this applies to the casesin FIGS. 2A-3D, or 2) The materials are externally magnetized in adirection that is perpendicular to the small AC magnetic modulation.

The latter scenario is tested in FIG. 5A. The same coupons 221 (ferriteor martensite, 38.1 mm (L)×25.4 mm(W)×4.7 mm (H)) are magnetized acrossits longer edge with two neodymium permanent magnets 223 a, 223 b placedat the ends of the coupon 221. One of the magnets 223 a has its northpole facing up and the other one 223 b is in opposite orientation. Alarge carbon steel plate 225 is attached at the bottom to complete themagnetic flux loop. The bundle of transmitting and pickup coils 201, 203has a cross-section dimension of 1 inch by 2 inches, and we align theshorter side (1 inch) of the coil-bundle with the longer side (1.5inches) of the coupon 221 to avoid the interference with fringe fieldnear the ends, as in FIG. 5(A). In this scenario, the magnetization atthe center of coupon 221 is in horizontal direction while the small ACmagnetic modulation from the coil is in vertical direction. Theexperimental results are shown in Table 4, and for both ferrite andmartensite cases, all the peaks of harmonics experience very smallchanges before and after this perpendicular magnetization. In addition,the even numbers of harmonics are very small and similar to the noiselevel as in the baseline air case (1st line of the table), which isconsistent with our theoretical description.

This symmetry in hysteresis loop can be broken if the direction ofmagnetization is not perpendicular to the direction of AC modulation. Ifwe rotate the coil-bundle by 90 degrees horizontally and align itslonger side (˜2 inches) with the longer side of the steel coupon as inFIG. 5B, the AC magnetic modulation generated from the transmitting coil201 is strongly interfering with the fringe field at the end of thesteel coupon, and thus breaks the symmetry in the hysteresis loop andwould allow even numbers of harmonics. Compared to the steel couponswithout magnetization in the same configuration, in Table 4-5 we haveindeed observed experimentally an increase in the 2nd harmonics that isconsistent with our theory. In addition, the peaks for odd numbers ofharmonics are reduced by at least one order of magnitude.

FIGS. 5A and 5B show embodiments of a set up for testing nonlinearmagnetic response of model materials under strong external magneticfield. In the embodiment of FIG. 5A, when the shorter side ofcoil-bundle aligns with the longer side of steel coupon, the magneticmodulation is mostly perpendicular to the external magnetization insteel coupon. Thus the external magnetization does not change thenonlinear response, and the experimental results are summarized in Table4 below.

TABLE 4 Harmonics normalized to 1^(st) peak 2^(nd) 3^(rd) 4^(th) 5^(th)Harmonics Harmonics Harmonics Harmonics Air 4.71 × 10⁻⁸ 1.32 × 10⁻⁸ 3.92× 10⁻⁹ 2.91 × 10⁻⁹ Martensite 1.92 × 10⁻⁸ 1.32 × 10⁻⁷ 3.85 × 10⁻⁹ 8.97 ×10⁻⁹ without magnet Martensite with 4.67 × 10⁻⁸ 1.56 × 10⁻⁷ 2.41 × 10⁻⁹1.26 × 10⁻⁸ magnet Ferrite without 7.30 × 10⁻⁸ 2.91 × 10⁻⁶ 4.15 × 10⁻⁹8.69 × 10⁻⁸ magnet Ferrite with 4.03 × 10⁻⁸ 4.51 × 10⁻⁶ 7.20 × 10⁻⁹ 1.86× 10⁻⁷ magnet

In the embodiment of FIG. 5B, when the longer side of coil-bundle alignswith the longer side of steel coupon, the magnetic modulation stronglyinterferes with the fringe field in the steel and they are barelyperpendicular to each other. The symmetry breaking leads to a rise in2nd harmonics and a surprising depression of odd numbers of harmonics,as summarized in Table 5 below.

TABLE 5 Harmonics normalized to 1^(st) peak 2^(nd) 3^(rd) 4^(th) 5^(th)Harmonics Harmonics Harmonics Harmonics Air 4.71 × 10⁻⁸ 1.32 × 10⁻⁸ 3.92× 10⁻⁹ 2.91 × 10⁻⁹ Martensite 2.35 × 10⁻⁸ 4.58 × 10⁻⁷ 4.30 × 10⁻⁹ 2.43 ×10⁻⁸ without magnet Martensite with 2.63 × 10⁻⁷ 4.09 × 10⁻⁸ 2.07 × 10⁻⁹1.78 × 10⁻⁹ magnet Ferrite without 1.38 × 10⁻⁷ 3.60 × 10⁻⁵ 2.99 × 10⁻⁸1.07 × 10⁻⁶ magnet Ferrite with 3.95 × 10⁻⁷ 5.62 × 10⁻⁷ 1.45 × 10⁻⁹ 1.53× 10⁻⁸ magnet

To see a more pronounced symmetry breaking effect, a ferromagneticmaterial can be strongly magnetized and the external magnetization canbe removed afterwards. A test was performed using a sample of low carbonsteel that has a remanence or residual magnetization that is over halfthe value of saturation magnetization, which and is an model material.In FIGS. 6A-6C, a series of tests on this carbon steel sample wereperformed before and after magnetization. Before the low carbon steelplate is strongly magnetized, a significant increase in odd harmonics isdetected as shown in FIG. 6B similar to previous data in Table 1 and 2.The large carbon steel plate is then magnetized locally around aspecific point “B” with a 1.27 cm-cubic 0.8 Tesla Neodymium permanentmagnet. After removing the permanent magnet from the plate, the residualmagnetization near point “B” should be over 0.4 Tesla on the carbonsteel plate. Compared to the PSD of carbon steel before themagnetization (FIG. 6B), the nonlinear magnetic detection nearmagnetized area “B” shows a strong increase in even number of harmonicsin FIG. 6C. It is now clear that in addition to the steel phasedetection by odd numbers of harmonics, the detection of even numbers ofharmonics could provide additional materials information, such asmagnetization state of the materials, including the pre-existingresidual magnetization of the materials. FIGS. 6A-6C show Power SpectralDensity (PSD) results for nonlinear magnetic detection of air (FIG. 6A),low carbon steel plate (FIG. 6B), and low carbon steel plate aftermagnetization (FIG. 6C) as measured in a FIG. 2A configuration. Thedashed curve and solid curve are PSDs of pickup voltage and transmittingcurrent respectively. Table 6 summarizes normalized harmoniccoefficients for the pickup voltages across all the samples here.

TABLE 6 Harmonics normalized to 1^(st) peak 2^(nd) 3^(rd) 4^(th) 5^(th)Harmonics Harmonics Harmonics Harmonics Air (a) 3.25 × 10⁻⁷ 8.03 × 10⁻⁷4.44 × 10⁻⁸ 2.22 × 10⁻⁸ Martensite (b) 5.70 × 10⁻⁷ 1.97 × 10⁻⁴ 3.16 ×10⁻⁸ 8.23 × 10⁻⁷ Ferrite (c) 1.49 × 10⁻⁵ 4.30 × 10⁻⁴ 9.93 × 10⁻⁷ 1.61 ×10⁻⁶

In FIGS. 6A-6C, the pickup circuit was slightly modified to enhance thesignal-to-noise ratio around the 3rd harmonics (using a RLC bandpassfilter with resonance frequency at 30 kHz), and, as a result, thebaseline calibration in air environment experience stronger harmonicsfrom electronic noise while the ratios of higher order harmonics betweensamples are not altered.

In addition to the manipulation of magnetization of steel, the sampleswere tested at different frequencies, from 1 kHz to 100 kHz. A fewexamples with low carbon steel at 1 kHz and 10 kHz are shown in Table 7,and examples with 100 kHz are shown later in FIGS. 9D-F. Table 7 showsnormalized harmonic coefficients for nonlinear magnetic detection of airand carbon steel at 1 kHz and 10 kHz.

TABLE 7 Harmonics normalized to 1^(st) peak 2^(nd) 3^(rd) 4^(th) 5^(th)Harmonics Harmonics Harmonics Harmonics Air (10 kHz) 5.28 × 10⁻⁸ 2.50 ×10⁻⁸ 4.17 × 10⁻⁹ 3.70 × 10⁻⁹ Carbon steel 2.30 × 10⁻⁸ 1.39 × 10⁻⁵ 5.29 ×10⁻⁹ 3.33 × 10⁻⁷ (10 kHz) Air (1 kHz) 3.00 × 10⁻⁸ 9.00 × 10⁻⁹ 1.05 ×10⁻⁸ 3.55 × 10⁻⁸ Carbon steel 4.29 × 10⁻⁸ 1.12 × 10⁻⁶ 1.43 × 10⁻⁸ 1.72 ×10⁻⁷ (1 kHz)

With a frequency-dependent skin depth of conductive materials

$d_{p} = \sqrt{\frac{1}{\pi \; f\; {\mu\sigma}}}$

and the complicated dynamics of magnetic domain walls, it is hard topredict the frequency dependency of the nonlinear magnetic response.However, our experiment demonstrated it is possible to measure asignificant nonlinear magnetic response in ferromagnetic materialsacross the frequency band from 1 kHz to 100 kHz, and thisfrequency-dependent response can be used to provide material informationfrom different depths.

In accordance with at least one aspect of this disclosure, embodimentsinclude, but not limited to, using an external magnetic field toregulate nonlinear magnetoacoutic detection. A computer simulation wasperformed to demonstrate the functioning of such embodiments. Althoughthe symmetry breaking effects lead to the generation of even numbers ofharmonics, which could be useful to probe the residual magnetization ofsteel, the effects on odd numbers of harmonics can be relativelycomplicated. Both enhancement of 3rd harmonics as in FIGS. 6B and 6D andreduction of 3rd harmonics as in FIG. 5B have been observed. Referringto FIGS. 7A-7C, which illustrate without limiting the embodiments of amethod of regulating magnetization in a steel pipe to achieveconsistency in measurements and avoid such potential complications isdescribed. Embodiments of the method involve an external magnetic fieldapplied by a horseshoe magnet with magnetization of 10⁵ A/m anddimensions specified in the legend of FIG. 7A. COMSOL multiphysicscomputer software package can be used to simulate the magnetic fieldstrength when the horseshoe magnet is moving vertically along the pipewall at a speed of 0.5 m/s, for example. FIGS. 7B and 7C show thespatially varying induced magnetic field.

FIG. 7A shows an embodiment of a moving horseshoe magnet 700 on a steelpipe 701. Regions 703 and 705 are squares with width 3 cm. Region 707has a vertical length of 4 cm. Region 709 has an inner diameter of 2 cmand outer diameter of 5 cm. The pipe is axial symmetric with a radius of15 cm and thickness of 8 mm. The pipe composed of ferrite phase exceptfor a circular region 711 of radius 3 mm. The magnet is movingvertically up at a speed of 0.5 m/s. FIG. 7B shows a verticalz-component of magnetic flux density in the horseshoe magnet and pipewall. FIG. 7C shows an embodiment a horizontal r-component of magneticflux density in the horseshoe magnet and pipe wall.

The magnetic field in the steel pipe between the legs of horseshoe isalmost along the vertical z-direction (|B_(z)|˜−0.2 to 0.4 T) with aminor perturbation of |B_(r)|˜up to 0.8*10⁻² T in the horizontaldirection owing to the small hard phase defect and the hysteretic natureof the material. As a result, this external magnetic regulation couldeffectively modify and align the magnetization in steel pipe along thevertical axis near the circular region 711 in FIG. 7A, and a smallperpendicular AC magnetic modulation based on this configuration wouldbe one of the preferred implementation in pipeline application as itleads to a unique and comprehensible 3rd harmonic signature asdemonstrated in FIG. 5A.

Referring now to FIGS. 8A and 8B, along with nonlinear magneticdetection, embodiments herein include nonlinear magnetoacousticdetection based on the same principle. FIG. 8A shows an embodiment of asetup 800 for nonlinear magnetoacoustic detection. A large carbon steelplate 801 (6 inches by 2 inches by 0.5 inch) can be magnetized with twoNeodymium permanent magnets 803 a, 803 b, for example. A carbon steelrod 805 (or any other suitable material rod) can be attached to theopposite sides of permanent magnets 803 a, 803 b to complete magneticflux loop. An acoustic transducer 807 can be attached (e.g., glued) tothe front center of the 6-by-2-inches surface of the carbon steel plate801, and the current transmitting coil (not illustrated) can be attachedto the back center of the opposing surface of the carbon steel plate.

When a large carbon steel plate is magnetized with two Neodymiumpermanent magnets attached as in FIG. 8A, there is a strong DC magneticfield B_(DC)({right arrow over (r)}) inside the carbon steel plate. Oncea small AC magnetic modulation is applied with the transmitting coil,the time varying magnetic fields generates an oscillating Eddy currentJ_(eddy)({right arrow over (r)}, t), which interacts with strong DCmagnetic field, resulting in an oscillating Lorentz body force f({rightarrow over (r)}, t)=J_(eddy) ({right arrow over (r)}, t)×B_(DC)({rightarrow over (r)}) and mechanical motion. This coupled response iscommonly called magnetoacoustic response, and the mechanical motion ismeasured through an acoustic sensor such as a piezoelectric acoustictransducer.

FIG. 8B shows the experimental PSD results for nonlinear magnetoacousticdetection. The dashed curve and solid curve are PSDs of receivedacoustic signals and transmitting current respectively. As thetransducer used for simulation has a resonance frequency of 500 kHz, themechanical motion was barely measurable for 10 kHz magnetic modulation.A 100 kHz magnetic modulation was used instead, and a strong 3rdharmonics generation in the PSD of acoustic signal (dashed curve in FIG.8B) was observed. As discussed above, weaker 3rd harmonics also show upin the PSD of transmitting current (solid curve in FIG. 8B) due to thechange in self-inductance.

The implementation or design of the non-destructive material inspectionsystems described herein can include, but is not limited to, multiplecopies of magnetic transmitters, magnetic sensors, acoustic sensors, andhorseshoe magnets located at positions placed at a preferred nearbylocation of the interrogated material. In certain embodiments, suchimplementation includes, but is not limited to, one or more copies ofmagnetic sensors and/or acoustic sensors paired with one magnetictransmitter. In certain embodiments, a preferred arrangement includes 4copies of magnetic sensors and/or acoustic sensors 900 at differentlocations around and/or paired with each magnetic transmitter 901 (shownin FIG. 9). A more preferred arrangement may include 8 copies ofmagnetic sensors and/or acoustic sensors 1000 at different locationsaround and/or paired with each magnetic transmitter 1001 (shown in FIG.10). An even more preferred arrangement may include maximum copies ofmagnetic sensors and/or acoustic sensors with different sizes and atdifferent locations around and/or paired with each magnetic transmitter.In certain embodiments, such implementation includes, but is not limitedto, at least one horseshoe magnet with its two legs contacting thesurface of interrogated material. In certain embodiments, suchimplementation includes, but is not limited to, at least one magnetictransmitter, and at least one of either magnetic sensor or acousticsensor located at the center of the horseshoe magnets. In certainembodiments, such implementation includes, but is not limited to, anoptional magnet or electromagnet to regulate the magnetization in theinterrogated material. In certain embodiments, such implementationincludes, but is not limited to, an optional magnet or electromagnet toprovide DC magnetic field.

In accordance with at least one aspect of this disclosure, embodimentscan be used without limitation for detection on real pipe with hardphase in the weld. Referring to FIGS. 11A-11F, embodiments can beapplied to detect anomalies in real pipeline steel, for example. Acylindrical pipe section about 10 cm long with a radius of 21 cm andthickness of 0.5 cm was tested, which was taken from a vintage, pre-70spipeline. The majority of the pipe has ferrite/pearlite phase, while theseam weld in the pipe was joined by electrical resistance weldingwithout heat treatment and thus it contains bainite or martensite hardsteel phase. During measurement, the longer side of the coil-bundle isaligned with the circumferential direction. The nonlinear magneticresponse at different angular positions was measured, both from insideand outside of the pipe section at 10 kHz magnetic modulation, and thenormalized 3rd harmonics coefficients are shown in FIGS. 11A and 11B.

FIG. 11A shows data of normalized 3rd harmonics coefficients around thecylindrical pipe section with 10 kHz magnetic modulation. The dashedcurve represents the measurements from outside of the pipe and the solidcurve represents the measurements from inside of the pipe. FIG. 11Bshows the same data in FIG. 11A plotted against circumferential distancefrom the seam weld. FIG. 11C shows data of normalized 3rd harmonicscoefficients with 10 kHz magnetic modulation, which was measured in aseparate experiment across an arc-shaped section of pipeline materialsthat does not have hard steel phase in its seam weld. The dashed curverepresents the measurements from outside of the pipe and the solid curverepresents the measurements from inside of the pipe.

In FIG. 11A, the measurement from outside of the pipe (dashed curve)shows a fluctuating 3rd harmonics around 1×10⁻⁵ in ferrite/ferritepearlite regions, and a dramatic decrease to almost 1×10⁻⁷ near the seamweld that contains bainite or martensite hard steel phase. The angularposition of the hard spot is identified as the minimal point in thedashed curve at 294.5 degrees, which is within 1 degree of the actualhard microstructure spot.

In embodiments where the coils are placed inside the pipe, the magneticflux lines inside the cylinder can be quite different and can be highlycompressed, which can alter the nonlinear measurement. The experimentalmeasurement from inside of the pipe indeed shows a different pattern of3rd harmonic responses (solid curve in FIG. 11A) and a double-minimalnear the weld. From symmetry consideration, the midpoint of the doubleminimal (293.2 degrees) may best describe the position of the measuredanomaly, which is also within 1 degree of the actual hard martensitespot. The quadruple pattern in the solid curve might come from aresidual magnetization of the materials, while the double-minimalfeature and the significantly lower harmonic response might result froma specific EM resonance mode inside the complete cylindrical pipe.

In comparison, in FIG. 11C we have tested an arc-shaped section ofpipeline materials that does not have a hard phase such as martensite orbainite phase in its seam weld. The measurements from outside and insideof the pipe section are shown respectively as the dashed and solidcurves in FIG. 11C. As this cut section is arc-shaped and not a completecylindrical shape, the results from inside and outside are similar.Although both data show certain extent of reduction of 3rd harmonicsaround the actual weld flash (between 49 mm to 63 mm), these anomalies(coefficient ˜1×10⁻⁶) are yet not significant enough to indicate thepresence of hard phase such as martensite or bainite, which has adistinguishing signature close to 1×10⁻⁷. Instead, a small crack ofdepth about 1 mm at outer surface of the weld flash was observed, and,as a result, the changes of 3rd harmonics in FIG. 11C can be usedindicate the presence of air gaps, cracks or different stress statesaround the weld.

These same pipe sections are also tested with 100 kHz AC magneticmodulation, and the data are shown in FIGS. 11D-E for the cylindricalpipe section, and in FIG. 11F for the arc-shaped pipe section. FIGS.11D-11F shows similar measurements as in FIGS. 11A-11C, but with 100 kHzmagnetic modulation and measured only from outside of the pipematerials. For the cylindrical pipe section, the measurements fromoutside of the weld show a distinguishing feature around the weld thatcontains hard phase such as martensite or bainite phase (FIGS. 11D and11E). In comparison, for the arc-shaped pipe section, the measured curveof nonlinear magnetic response is rather flat as the weld contains onlyferrite or ferrite-pearlite phase with a small crack.

FIGS. 12A-12C show embodiments of the detection and differentiationbetween nonhysteretic material and nonhysteretic material withinhomogeneities of hysteretic ferromagnetic materials. In the tests ofFIGS. 12A-12C, the system 200 can be configured for use on a single sideof the interrogated material shown in FIG. 12B. As presented above, incertain embodiments, the one or more conditions of the material to bedetermined can include one or more specific material phases, forexample. Example results for determining material phases between anonhysteretic material and a nonhysteretic material with inhomogeneitiesof hysteretic ferromagnetic materials are shown in FIGS. 12A-12C.

As a control experiment in FIG. 12A, the device 200 was tested at 10 kHzfrequency in air without any conducting/magnetic materials within half ameter. The electrical current used here is lower than what is used inFIG. 2B-D and FIG. 3B-D to reduce electronic noise floor. The powerspectral densities (PSDs) of pickup voltages are shown. The peaks ofhigher order harmonics (2nd, 3rd, and 4th, etc.) are at least 9 ordersof magnitude lower than the primary frequency of 10 kHz. These smallvalues of harmonics are due to electronic processing and system noise,and should be calibrated as a baseline for specific material testing.

As can be seen in these examples from FIGS. 12A-12C, both even and oddharmonics show orders of magnitude differences between the nonhystereticmaterial (FIG. 12B) and the nonhysteretic material with inhomogeneitiesof hysteretic ferromagnetic materials (FIG. 12C), allowing foridentification of different materials, for example. Nonlimiting examplesof nonhysterestic materials include austenitic stainless steel, duplexstainless steel, and high manganese steel. Nonlimiting examples ofnonhysteretic material with inhomogeneities of hysteretic ferromagneticmaterials include high manganese steel with epsilon martensiteinclusions. FIGS. 12A-12B show that the nonlinear magnetic response doesnot change dramatically when the end of coils are placed on a plate ofnonhysteretic material (e.g., 200 mm (L)×200 mm (W)×20 mm (H)). This isconsistent with the fact that a nonhysteretic material is a linearmagnetic material with constant magnetic permeability, and as a resultit does not generate any nonlinear magnetic response. FIGS. 12A and 12Cshow that the nonlinear response changes dramatically when the end ofcoils are placed on a plate of nonhysteretic material withinhomogeneities of hysteretic ferromagnetic materials (e.g., 200 mm(L)×200 mm (W)×20 mm (H) with over 5% inhomogeneities by weight inmaterial weight fraction). The peaks for both odd and even numbers ofharmonics increase dramatically. In particular, compared tononhysteretic material in FIG. 12B, the peak of 3rd harmonics in FIG.12C increases by two orders of magnitude with the nonhysteretic materialwith inhomogeneities of hysteretic ferromagnetic materials, providingunique nonlinear magnetic signatures that can be directly utilized todetect nonhysteretic material with inhomogeneities of hystereticferromagnetic materials.

Similar to the common practice in other non-destructive inspection tool,one familiar with the technique can calibrate the nonlinear magneticresponse and/or the peak value of 3^(rd) harmonics with respect todifferent fractions of inhomogeneities of hysteretic ferromagneticmaterials in a nonhysteretic material. As such, with propercalibrations, the methods and systems of the present disclosure can beused to measure the material phase fractions of a sample with two ormore material phases, such as a nonhysteretic material withinhomogeneities of hysteretic ferromagnetic materials.

In accordance with at least one aspect of this disclosure, embodimentscan be used without limitation for detection of undesirable phases onthe surface and/or in the bulk of real TMCP steel plate and/or pipe.Referring to FIGS. 13A-13E, embodiments can be applied to detectanomalies in real pipeline steel, for example. A curved pipe section wascut from a TMCP pipe (28″ inner-diameter (ID) and about ¾ inch thick),and about 4″ by 4″ area of the pipe section was tested. The majority ofthe pipe has ferrite/pearlite and/or softer granular bainite phase,while part of the ID surface contains lath bainite or martensite hardsteel phase that naturally formed during the TMCP manufacturing processat the steel mill.

When the longer side of the coil-bundle comprising a magneticsensor/acoustic sensor 1300 and a magnetic transmitter 1301 is alignedwith the horizontal direction as shown in FIG. 13A (also thecircumferential direction of the pipe), a data map of the normalized3^(rd) harmonics is shown in FIG. 13A. When the longer side of the samecoil-bundle is aligned with the vertical direction as shown in FIG. 13B(also the longitudinal direction of the pipe), a data map of thenormalized 3^(rd) harmonics is shown in FIG. 13B. FIG. 13C is a data mapwith combined data sets from both FIGS. 13A and 13B and at any specificlocation FIG. 13C only uses the lower value of the normalized 3^(rd)harmonics between FIGS. 13A and 13B.

On the same pipe section, two different anomaly-zones show up with twodifferent transmitter-sensor orientations, a white to light grey zonearound the top-left of FIG. 13A and a white to light grey zone aroundbottom-right of FIG. 13B. To validate that both zones from differenttransmitter-sensor orientations are consistent with actual materialhardness properties, the TMCP pipe section was cut and ten crosssectioned material samples were made from different parts of the pipesection. Those samples are then metallographically polished and VickersHardness (VHN) measurements are performed in the cross-section with100-gram load at 100 μm below the surface by indentation. For example,one of the cross-sectioned samples is cut from location of the box 13Din FIG. 13E, and the corresponding Vickers Hardness (VHN) measurementsfor the specific sample are shown in FIG. 13D in a one-dimensionmeasurement bar as well as a simple data plot. FIG. 13E demonstrates theensemble of ten VHN results. The hardness measurement bars are placed atthe locations where cross sectioned samples were cut from.

Consistent with the Vickers Hardness measurements, the nonlinearmagnetic response in particular normalized 3^(rd) harmonics data maps(FIGS. 13A-13C) are able to capture both the top-left and bottom-righthard zones as validated in FIG. 13E. Specifically the data with thetransmitter-sensor orientations in FIG. 13A and FIG. 13B are able tocapture respectively the top-left and bottom-right hard zones in FIG.13E. The data anisotropy comes from the intrinsic texture anisotropy incarbon steel generated from the manufacturing process such as hotrolling process, and in order to achieve better and more completeinspection results, a preferred transmitter-sensor arrangement mayinclude many copies of sensors at different locations around and/orpaired with each magnetic transmitter.

In the embodiment shown, the transmitting coil 201 and pickup coil 203used to produce the data below include coils with a maximum outerdiameter of about ¾ inch and an inductance of L˜7 mH. For the data shownfrom FIGS. 14A-14C, the transmitting coil 201 and pickup coil 203 areplaced to the same side of the interrogated material (e.g.,ferromagnetic plate).

The coils with smaller diameter work in a similar fashion as previouslydisclosed 1-inch coils as shown in FIGS. 2B-D and FIGS. 3B-D. As acontrol experiment, the device 200 was tested at 10 kHz frequency in airwithout any conducting/magnetic materials within half a meter. The powerspectral densities (PSDs) of the pick up voltages are shown in FIGS.14A-14C. The peaks of higher order harmonics (2nd, 3rd, 4th, and 5th,etc.) are at least 8 orders of magnitude lower than the primaryfrequency of 10 kHz in the air case (FIG. 14A). These small values ofharmonics are due to electronic processing and system noise, and shouldbe calibrated as a baseline for material testing.

Similar to the disclosure from FIGS. 2B-D to FIGS. 3B-D, odd harmonicsshow orders of magnitude differences between the different materialtypes, allowing for identification of different materials, for example.The nonlinear response changes dramatically once a coupon of martensiteor ferrite (e.g., 38.1 mm (L)×25.4 mm(W)×4.7 mm (H)) is placed at theend of smaller coils. The even numbers of harmonics do not experiencesignificant changes, while the peaks for odd number of harmonicsincrease dramatically, with the most significant increases coming from3rd and 5th harmonics at 30 kHz and 50 kHz (e.g., in FIGS. 14B and 14C).In particular, the peak of 3rd harmonics increases by over three ordersof magnitude with a martensite coupon (FIG. 14B) and over five orders ofmagnitude with ferrite coupon (FIG. 14C), providing unique nonlinearmagnetic signatures that can be directly utilized to detect the hardphases such as martensite phase that make up the hard spots in pipelinesteel, for example.

In accordance with at least one aspect of this disclosure, thesmaller-diameter magnetic transmitters and sensors can be used togenerate inspection results with higher lateral spatial resolution. Inthe embodiment shown, the transmitting coil 201 and pickup coil 203 usedto produce the data below include coils of ¾ inch diameters as used inFIGS. 15A-15B. Both the transmitting coil and the pickup coil aremounted onto a carriage of a two-dimensional automated scanner. Thetwo-dimensional automatic scanner is capable of moving a carriage in aflat horizontal plane with a minimal step-size smaller than 0.1 mm ineither dimension, and the two-dimensional spatial motions and locationsof the carriage and/or the coils can be controlled and monitored throughcomputer program codes.

In accordance with at least one aspect of this disclosure, embodimentscan be used without limitation for detection on real pipes and plateswith spatially varying hard phase on the surface and/or in the bulk.Referring to FIGS. 15A-15B, embodiments can be applied to detectanomalies in carbon steel plate, for example. A flat 4140 carbon steelplate (e.g., 12″ (L)×6″ (W)×1¼ (H)) was tested as shown in FIG. 15Aright panel. The majority of the plate has ferrite/pearlite phase, whilethere are seven horizontal streaks of hard phase regions or hard zones.These simulated hard zones are made with local surface heating usingelectron beam in vacuum environment followed by fastself-temperature-quenching with the steel body as a heat sink. Theheating parameters used in HZ1 to HZ7 are different, thus these sevenhard zones have different local hardness and widths, and they containdifferent volume fractions of lath bainite or martensite hard steelphase.

During measurements with the two-dimensional automated scanner, thetransmitting and pickup coils are placed within 0.1 cm to the surface ofthe interrogated sample, and the longer side of the coil-bundle isaligned with the longer direction (12″) of the plate direction. Thenonlinear magnetic responses at different two-dimensional positionsacross the whole steel plate were measured at 10 kHz magneticmodulation, and from the measurements a data map of the normalized 3rdharmonics coefficients is shown in FIG. 15A left panel. As detailed inFIG. 15A left panel, darker grey indicates higher value of normalized3^(rd) harmonics (softer in material properties) and white indicateslower value of normalized 3^(rd) harmonics (harder in materialproperties). All seven hard phase regions (HZ1 to HZ7) are detected bythe nonlinear magnetic response measurements with different levels of3^(rd) harmonics among them.

To validate the nonlinear magnetic response measurements and theresulting data map are consistent with material hardness properties, the4140 carbon steel plate was cut along the dash line 15B as in FIG. 15Aright panel. Along the dash line, 15B seven cross sectioned materialsamples were made and metallographically polished and Vickers Hardness(VHN) measurements are performed in the cross-section with 100-gram loadat 100 μm below the surface by indentation. The hardness measurementsacross HZ1 to HZ5 along the dash line 15B are shown in FIG. 15B rightpanel. For HZ6 and HZ7, the hardness measurements do not capture anyelevated hardness when measured at 100 μm below the surface,demonstrating that both HZ6 and HZ7 do not have elevated hard zones at100 μm or deeper. In accord with the Vickers hardness measurements, thenonlinear magnetic response in particular normalized 3^(rd) harmonicsare plotted along the same dash line 15B and the results are shown inFIG. 15B left panel, the data of normalized 3^(rd) harmonics are able tocapture all HZ1 to HZ7 with consistent correlations of height and widthof results. Specifically, the FWHM (Full width at half maximum) widthsare labeled for all the measured hard zones for both the 3^(rd)harmonics responses and the hardness measurements. The widths measuredfrom 3^(rd) harmonics responses are within 1 mm to 2 mm variations fromwidths measured from the hardness measurements which are generallyconsidered as ground truth. In the embodiment shown, the nonlinearmagnetic response is capable of detecting surface hard zone with alateral spatial resolution of 2 mm or greater.

Referring to FIGS. 16A-16B, embodiments can be applied to detectanomalies in carbon steel plate, for example. Referring to FIG. 16A leftpanel, a flat TMCP carbon steel plate (e.g., 9″ (L)×5″ (W)×1″ (H)) wastested. The majority of this plate has ferrite/pearlite and/or softgranular bainite phase, while there are four vertical streaks of hardphase regions or hard zones, the centers of which are labeled with crossmarker signs on the plate. These simulated hard zones are made withlocal surface heating using electron beam in vacuum environment followedby fast self-temperature-quenching with the steel body as a heat sink.The heating parameters used here are the same parameters used for HZ2 toHZ5 in previous plate (FIG. A14), thus these four hard zones havedifferent local hardness and widths, and they contain different volumefractions of lath bainite or martensite hard steel phase. With the sameheating parameters, the hardness in HZ2 to HZ5 between 4140 carbon steeland TMCP carbon steel are also different as the chemistry of base steelplates are different.

With the same two-dimensional automated scanner, from the nonlinearmagnetic response measurements a data map of the normalized 3rdharmonics coefficients is shown in FIG. 16A right panel. As detailed inFIG. 16A right panel, black to dark grey indicates higher value ofnormalized 3^(rd) harmonics (softer in material properties) and white tolight grey indicates lower value of normalized 3^(rd) harmonics (harderin material properties). All four hard phase regions (HZ2 to HZ5) aredetected by the nonlinear magnetic response measurements with differentlevels of 3^(rd) harmonics among them.

To validate and test the sensitivity of the nonlinear magnetic responsemeasurements are consistent with material hardness properties, the TMCPcarbon steel plate was cut along the dash line 16B as in FIG. 16A leftpanel. Along the dash line 16B, one cross sectioned material sample wasmade and metallographically polished and Vickers Hardness measurementsare performed in the cross-section with 100-gram load at 100 μm belowthe surface by indentation. As an example, a cross-section hardness mapacross HZ3 is shown in FIG. 16B top panel. In the cross-section, theelevated hard zone has a semi-elliptical shape with a width of about 8.0mm and depth of 1.1 mm with an average increment of 40 in VickersHardness within the hard zone (VHN larger than 250). The materialmicrostructure in bulk region (VHN smaller than 250) is a mixture ofgranular bainite and acicular ferrite as shown in the scanning electronmicroscope image (FIG. 16B bottom left), and the material microstructurein the elevated hard zone (VHN larger than 250) is a mixture of granularbainite and lath bainite as shown in FIG. 16B bottom right. In accordwith the Vickers Hardness measurements, the FWHM width for HZ3 from the3^(rd) harmonics responses are determined to be about 10.0 mm across thesame dash line 16B, consistent with the hardness measurements with 2 mmspatial resolution.

Similar to the common practice in other non-destructive inspection tool,one familiar with the technique can calibrate the nonlinear magneticresponse and/or the peak value of 3^(rd) harmonics with respect todifferent levels of Vickers Hardness (VHN), surface area sizes and thedepth of hard metallurgical phase in a sample. As such, with propercalibrations, the methods and systems of the present disclosure can beused to measure the Vickers Hardness as well as the material phasefractions of a sample with two or more material phases, such as ahysteretic material with inhomogeneities of hard metallurgical phase.

The foregoing methods can be extended to the inspection of other steelcomponents including, but not limited to, bolts, forgings, castings, andthe like.

In accordance with at least one aspect of this disclosure, embodimentscan be used without limitation for detection of hysteretic magneticmaterial phases in nonhysteretic materials. Nonhysteretic materials caninclude, but is not limited to, aluminum, austenitic stainless steel,duplex stainless steel, and high manganese steel. Example of hystereticmagnetic material phases include, but are not limited to, at least oneof martensite, epsilon martensite, ferrite, pearlite, bainite, lathbainite, acicular ferrite, and quasi-polygonal ferrite. A first exampleapplication of the detection of hysteretic magnetic material phases innonhysteretic materials includes determining an amount of magneticferrite content in duplex stainless steels (DSS), which can be used forgrading the DSS or as a quality control measure. More specifically, theamount of delta ferrite in a ferrite-austenite DSS can be ascertainedand used to grade the ferrite-austenite DSS or as quality control todetermine if the amount of delta ferrite fall within a desired range.

In yet another example, the detection of hysteretic magnetic materialphases in nonhysteretic materials can be used for quality control whenaustenitic stainless steel (e.g., grades 304, 308, 316, and the like)weldments and austenitic stainless steel welds are exposed to hightemperatures, for example, when refinery operating equipment such aspiping, vessels, reactors, and weld overlays is exposed to hydrotreatingconditions or hydroprocessing conditions. Under such conditions, thesigma phase (e.g., of ferrite) (a hysteretic magnetic material phase)can form, which causes the material to become brittle. The methods anddevices described herein can be used to measure the amount of or detectthe presence or absence of the embrittling sigma phase in all orportions of the refinery operating equipment. In hydrotreating,typically, the refinery operating equipment and welds thereof containaustenitic stainless steels. In hydroprocessing, typically, the refineryoperating equipment downstream of the reactor contains austeniticstainless steels, and the welds in refinery operating equipmentupstream, in, and downstream of the reactor are contain austeniticstainless steels. The reactor in hydroprocessing is typically composedof Cr—Mo materials with austentic steel weld overlays. In someembodiments, the methods and devices described herein can also be usedto measure the amount of or detect the presence or absence of ferritecontent in girth and seam welds that are used for fabrication ofaustentic stainless steel piping, vessels and weld overlay of heavy wallCr—Mo reactors in hydroprocessing reactors in D/S. The amount of ferritecontent needs to meet a desired amount for preventing weld solificationcracking in stainless steel weldments.

In each of the foregoing examples of detecting hysteretic magneticmaterial phases in nonhysteretic materials, calibration samples can beprepared with different amounts of hysteretic magnetic material phasesin nonhysteretic materials to correlate the nonlinear magnetic responsesignal to the amount or content of the hysteretic magnetic materialphases.

In accordance with at least one aspect of this disclosure, embodimentscan be used without limitation for characterizing the hardness of welds.Similar to the disclosure regarding FIGS. 13A-E, the VHN or BrinellHardness number (BHN) of different weld materials can be correlated tothe nonlinear magnetic response signal described herein. In a firstexample of applying the characterization the hardness of welds, ahandheld device can be used to measure the nonlinear magnetic responsesignal to welds (new, old, or repaired) or portions thereof, which canthen be correlated to a VHN and/or a BHN.

Another example of applying the characterization the hardness of weldsis to identify the type of electric resistance weld (ERW) (e.g.,low-frequency heat-treated ERW, low-frequency non-heat-treated ERW,high-frequency heat-treated ERW, and high-frequency non-heat-treatedERW). In this example, the nonlinear magnetic response signal base pipeas compared to the nonlinear magnetic response signal of the ERW cancorrelate to the type of ERW. Such correlation can be determined viastandard calibration measurements. Implementation of such methods can bewith in-line pipeline inspection gauges, automatic or manually pulledpipeline inspection tools, steel mill inspection tools, in-the-ditchinspection tools, handheld inspection devices, and the like. In yetanother example of applying the characterization the hardness of weldsis to identify the hardness of base pipe and the pipe grade usingin-the-ditch inspection. In this example, the nonlinear magneticresponse signal can be calibrated and correlated to hardness, tensileand/or yield strength of the materials of base pipe. Such correlationcan be used to determine the pipe grade using in-the-ditch inspection.

In yet another example of applying the characterization the hardness ofwelds, the hardness of welds (e.g., seam welds and/or girth welds) afterrepair. In one example, the repaired welds may be associated withpressure vessels (e.g., composed of Cr—Mo ½ Cr steels) used inhydrotreating and hydroprocessing reactors. The repair process caninclude removing the weld and a portions metal around the weld andreplacing/patching the area. The newly formed welds can optionally beheat treated. The inspection process can include determining if thewelds after repair (with or without post-weld heat treatment) meetindustry standards and/or company specifications for the hardness of theweld and/or identify hard spots in the weld.

Another similar example includes measuring the hardness of weldsassociated with 21/4 Cr—V steel vessels. The inspection process caninclude determining if fabrication welds and/or welds after a repair(with or without post-weld heat treatment) meet industry standardsand/or company specifications for the hardness of the weld and/oridentify hard spots in the weld.

Yet another similar example includes management of weld hardness overtime. That is, the vessels, pipes, and the like can be inspected overtime monitoring the hardness and/or location and size of hard spots.Inspection can be carried out with any suitable device include handhelddevices and automated crawlers. The inspection process can be performedon fabrication welds and/or repaired welds (with or without post-weldheat treatment).

In another embodiment of using the nonlinear magnetic response signalcorrelated to weld hardness and/or hard spots in a weld, weld rootsand/or weld caps specifically can be inspected and analyzed. In apreferred instance, this application can be applied to in-field welds ofrisers and sour service pipelines. Optionally, the inspection of rootwelds by the nonlinear magnetic response signal methods/devicesdescribed herein can be conducted in combination with laser rootprofiling. Increased hardness in a root weld (e.g., a girth weld root)can originate from high cooling rates in an improper weld procedures(e.g., using Cu cooled shoes to close to the weld root) and/or dissolvedCu contamination in the weld metal from equipment such as Cu cooledshoes).

In yet another example of using the nonlinear magnetic response signalcorrelated to weld hardness and/or hard spots in a weld, the quality ofback welds can be assessed. Back welds are internal repairs to girthwelds that are made manually. Determining the hardness and/or locationand size of hard spots in a back welds can verify if the back weld meetsthe industry standards and/or company specifications for the hardness ordetermine if further repair is needed. Implementation of such methodscan be with in-line pipeline inspection gauges, automatic or manuallypulled pipeline inspection tools, handheld inspection devices, and thelike.

In another example of using the nonlinear magnetic response signalcorrelated to weld hardness and/or hard spots in a weld, methods anddevices described herein can be used in conjunction with welding bugsused to produce girth welds and/or ultrasonic testing bugs used toinspect girth welds. Bugs are automated machinery that moves around thecircumference of a pipe to produce girth welds and/or inspect girthwelds. The devices described herein can be incorporated with bugs tomeasure the nonlinear magnetic response signal of the girth weld afterbeing formed (i.e., with a welding bug) or when also measuring theultrasonic response of the girth weld (i.e., with an ultrasonic testingbug).

In accordance with at least one aspect of this disclosure, embodimentscan be used without limitation for characterizing the hardness, tensilestrength, and/or yield strength of the material used to produce or inpipes or similar structures. Similar to the disclosure regarding FIGS.13A-E, the hardness (e.g., VHN or BHN), tensile strength, and/or yieldstrength of different materials used to produce or in pipes or similarstructures can be correlated to the nonlinear magnetic response signaldescribed herein. Once a hardness, tensile strength, and/or yieldstrength is determined, the pipe grade can be derived. Implementation ofsuch methods can be with in-line pipeline inspection gauges, automaticor manually pulled pipeline inspection tools, steel mill inspectiontools, in-the-ditch inspection tools, handheld inspection devices, andthe like.

In accordance with at least one aspect of this disclosure, embodimentscan be used without limitation for detecting and locating hard zones(e.g., cold worked areas or dents) that can cause stress corrosioncracking that lower the integrity of pipeline and similar structures.Stress corrosion cracking is the formation of or growth of a crack in acorrosive environment. In austenitic stainless steel and aluminumalloys, chlorides (e.g., NaCl, KCl, and MgCl₂) can be the source ofstress corrosion cracking. Stress corrosion cracking typically startwith a small flaw in the surface that propagates under conditions wherefracture mechanics predicts failure should not occur. Being able todetect stress corrosion cracking and/or regions of local hard workedzones (hard zones) that can cause stress corrosion cracking with anondestructive material inspection method or tool could mitigate thefailure pipeline or other structures. Implementation of such methods canbe with in-line pipeline inspection gauges, automatic or manually pulledpipeline inspection tools, handheld inspection devices, and the like.

As will be appreciated by those skilled in the art, aspects of thepresent disclosure may be embodied as a system, method or computerprogram product. Accordingly, aspects of the this disclosure may takethe form of an entirely hardware embodiment, an entirely softwareembodiment (including firmware, resident software, micro-code, etc.) oran embodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the this disclosure may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but is not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, or device, or any suitable combinationof the foregoing. More specific examples (a non-exhaustive list) of thecomputer readable storage medium would include the following: anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing. In the context of this document,a computer readable storage medium may be any tangible medium that cancontain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but is not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but is not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thethis disclosure may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like, conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages, and visual programming languages, such as LabViewor similar programming languages. The program code may execute entirelyon the user's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider). In certain embodiment, for example in current pipelineinspection gauge (PIG) technology, an on-board computer and processor onthe PIG is sent through the pipeline, during which time the computer usepre-loaded instructions and program codes to control the onboardtransmitters and sensors, perform initial analysis, and stores themeasurement results. At the pipeline outlet, the users retrieve the PIGand download the stored data, which can be further analyzed andpost-processed on another computer with different program codes.

Aspects of this disclosure are described above with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified herein.

Through laboratory experimentation and computer simulation, nonlinearmagnetic and magnetoacoustic systems and methods for detecting anddistinguishing ferromagnetic materials with different hysteresis curves,e.g., differentiating hard martensite spot from soft ferrite phase, havebeen disclosed. Examples of hysteretic materials include ferromagneticmaterials (e.g., steel, nickel, cobalt, etc.) and some of their alloys,such as a variety of carbon steels. It has also been observed that thenonlinear magnetic responses depend on the initial/residualmagnetization of the materials, and to avoid such complication,embodiments include an effective approach to regulate magnetizationinside the material. An example of such an effective approach, withoutlimitation, has been provided in the above discussions as in FIGS. 7A,7B and 7C, in which the materials are externally magnetized in adirection that is perpendicular to the small AC magnetic modulation.

Additionally, based on the fundamental electromagnetism, a naturalderivative of the nonlinear magnetic response is the nonlinearelectrical Eddy current generation. Once coupled with a large permanentmagnetic field, this Eddy current produces a nonlinear mechanical wave,producing a magnetoacoustic response with hysteretic materials that hasbeen evaluated. To improve the detection of magnetic anomalies (e.g., inpipeline inspection), nonlinear magnetic embodiments can be incorporatedinto an MFL setup within a conventional PIG system, and nonlinearmagnetoacoustic detection embodiments can be applied on existing EMATsensors, as appreciated by those having ordinary skill in the art.

Embodiments provide unprecedented nonlinear magnetic and magnetoacousticdetection to identify flaws and hard spots/regions in a pipe, forexample. Embodiments provide highly distinguishable features todifferentiate various hysteretic materials (soft ferrite steel/regionsand hard martensite steel/regions, for example) enabled by an in-depthunderstanding of the nonlinear magnetic response. In particular, botheven and odd harmonic responses have been investigated and theirrelationship to the magnetic properties and states of materials has beendiscovered. In addition, embodiments are highly favorable for fieldapplications because the method can be used across a wide frequency band(e.g., 100 Hz to 1 MHz), which can be highly favorable for high-speedinspection and depth scan, and embodiments operates at low current andlow magnetic field without any metal core and are thus relatively energyefficient.

Improvement in nondestructive pipeline inspection significantly reducesrisk of pipeline failures and leakage. Embodiments provide a new tool inthe arsenal of methods for pipeline inspection.

The methods and systems of the present disclosure, as described aboveand shown in the drawings, provide for nondestructive materialinspection with superior properties. In one application, the methods andsystems can be used as a nondestructive evaluation tool forin-line-inspection to identify material phases and assess regions withhigher hardness, or metal loss, or cracks from inside of the pipe. Inanother application, the methods and systems can be used as anondestructive evaluation tool to screen metal plates by identifyingmaterial phases and assessing regions with higher hardness, or metalloss, or cracks from surfaces of plates. Yet in another application, themethods and systems can be used as a handheld device to screen metalpipes, plates, surfaces, welds and joints by identifying material phasesand assessing regions with higher hardness, or metal loss, or cracksfrom surfaces of the metal object. Yet in another application, themethods and systems can be used as nondestructive evaluation tool toidentify steel phases in pipeline welds, welding types and/or heattreatment states of pipelines with electrical resistance welding (ERW).Additionally, in another application, the methods and systems can beused as a nondestructive evaluation tool to inspect girth weld roots byidentifying material phases and assessing regions with higher hardness,or metal loss, or cracks for risers, and sour service pipelines.

In the above mentioned applications, the material phases can include,but are not limited to, at least one of austenite, martensite, ferrite,pearlite, bainite, lath bainite, acicular ferrite, and quasi-polygonalferrite. In certain embodiments, the systems can be incorporated ontonondestructive evaluation tools to interrogate the material with aninput time varying magnetic field and correlating the time dependentnonlinear characteristic of the received magnetic response or acousticresponse to one or more material conditions of the material. Nonlimitingexamples of the nondestructive evaluation tools include in-line pipelineinspection gauges, automatic or manually pulled pipeline inspectiontools, steel mill inspection tools and handheld inspection devices.

In certain embodiments, the application can include, but is not limitedto, multiple copies of magnetic transmitters, magnetic sensors, acousticsensors and horseshoe magnets located at positions placed at a preferrednearby location of the interrogated material. In certain embodiments,the application includes, but is not limited to, one or more copies ofmagnetic sensors and/or acoustic sensors paired with one magnetictransmitter. In certain embodiments, a preferred arrangement includes 4copies of magnetic sensors and/or acoustic sensors at differentlocations around and/or paired with each magnetic transmitter (shown inFIG. 9). A more preferred arrangement may include 8 copies of magneticsensors and/or acoustic sensors at different locations around and/orpaired with each magnetic transmitter (shown in FIG. 10). An even morepreferred arrangement may include maximum copies of magnetic sensorsand/or acoustic sensors with different sizes and at different locationsaround and/or paired with each magnetic transmitter. In certainembodiments, the application includes, but is not limited to, at leastone horseshoe magnet with its two legs contacting the surface ofinterrogated material. In certain embodiments, the application includes,but is not limited to, at least one magnetic transmitter, and at leastone of either magnetic sensor or acoustic sensor located at the centerof the horseshoe magnets. In certain embodiments, the applicationincludes, but is not limited to, an optional magnet or electromagnet toregulate the magnetization in the interrogated material. In certainembodiments, the application includes, but is not limited to, anoptional magnet or electromagnet to provide DC magnetic field formagnetoacoustic response.

In certain embodiments, the application can include, but is not limitedto, a computer-controlled automatic moving platform to move the magnetictransmitters, magnetic sensors and acoustic sensors to detect magneticresponse or acoustic response at different spatial locations. In certainembodiments, the application can include, but is not limited to, amanually controlled translating and rotating platform to move themagnetic transmitters, magnetic sensors and acoustic sensors to detectmagnetic response or acoustic response at different spatial locations.In certain embodiments, the application can include, but is not limitedto, a handheld device that includes at least one magnetic transmitterand one magnetic sensor. In certain embodiments, interrogated sample inthe application can include, but is not limited to, low-frequencyheat-treated ERW pipes, low-frequency non-heat-treated ERW pipes,high-frequency heat-treated ERW pipes, and high-frequencynon-heat-treated ERW pipes.

EXAMPLE EMBODIMENTS

A first embodiment of the invention is a method for determining materialconditions of at least one hysteretic ferromagnetic material and/or atleast one nonhysteretic material, wherein the method comprises:interrogating the hysteretic ferromagnetic material and/or thenonhysteretic material with an input time varying magnetic field;detecting a magnetic response and/or acoustic response over time fromthe hysteretic ferromagnetic material and/or the nonhysteretic material;determining a time dependent nonlinear characteristic of the receivedmagnetic response and/or acoustic response; and correlating the timedependent nonlinear characteristic of the received magnetic responseand/or acoustic response to one or more material conditions of thematerial. Optionally, this embodiment can include one or more of thefollowing: Element 1: wherein the interrogation magnetic field includesadditional magnetic fields; Element 2: Element 1 and wherein theadditional magnetic fields includes a constant DC magnetic field;Element 3: wherein the interrogation magnetic field includes adegaussing magnetic field; Element 4: wherein the one or more materialconditions of the material is a material phase, and wherein the materialincludes at least one hysteretic ferromagnetic material; Element 5:wherein the one or more material conditions of the material is amaterial phase, and wherein the material includes at least onenonhysteretic material; Element 6: wherein the one or more materialconditions of the material is the presence of a nonhysteretic material,and wherein the material includes at least one hysteretic ferromagneticmaterial; Element 7: wherein determining the time dependent non-linearcharacteristic includes performing a frequency domain analysis thatincludes power spectral density analysis of the received magneticresponse and/or acoustic response to create power spectral density data;Element 8: Element 7 and wherein determining the time dependentnon-linear characteristic includes determining one or more harmonic peakvalues of the power spectral density data; Element 9: Element 8 andwherein determining the one or more harmonic peak values includesdetermining one or more harmonic coefficients of the spectral densitydata; Element 10: Element 9 and wherein determining the one or moreharmonic coefficients and/or peak values includes determining oddharmonic coefficients and/or peak values of the spectral density data;Element 11: Element 10 and wherein determining the odd harmoniccoefficients and/or peak values includes determining 3rd and/or 5thharmonics of the spectral density data; Element 12: Element 11 andwherein correlating the time dependent nonlinear characteristic includescomparing and correlating the 3rd and/or 5th harmonics to the one ormore material conditions; Element 13: Element 9 and wherein determiningthe one or more harmonic coefficients and/or peak values includesdetermining even harmonic coefficients and/or peak values of thespectral density data; Element 14: Element 13 and wherein determiningthe even harmonic coefficients and/or peak values includes determining2nd harmonics of the spectral density data; Element 15: Element 14 andwherein correlating the time dependent nonlinear characteristic includescomparing and correlating 2nd harmonics to additional materialsinformation including magnetization state of the materials and thepre-existing residual magnetization of the materials; Element 16:wherein the one or more material conditions include the presence of atleast a material phase of the hysteretic ferromagnetic material and/orthe nonhysteretic material; Element 17: wherein the hystereticferromagnetic material includes steel and wherein the material phaseincludes at least one of austenite, martensite, ferrite, pearlite,bainite, lath bainite, acicular ferrite, quasi-polygonal ferrite;Element 18: the method further comprising: wherein the one or morematerial conditions of the material are one or more first materialconditions of the material; repeating the steps of interrogating,detecting, determining, and correlating with the input time varyingmagnetic field in a different configuration to produce one or morematerial second conditions of the material; and combining the one ormore first material conditions and one or more material secondconditions of the material to produce combined data set that representsthe one or more material conditions; Example of combinations include,but are not limited to, Elements 1 and 3 in combination and optionallyin further combination with Element 2; two or more of Elements 4-6 incombination; Element 7, Element 8, Element 10 (optionally one or both ofElements 11 and 12), Element 13 (optionally with one or both of Elements14-15) in combination; Element 16 in combination with one or more ofElements 4-6 and optionally in further combination with Element 17;Elements 16 and 17 in combination; Element 18 in combination with one ormore of Elements 1-17; and any combination thereof.

Another embodiment of the present invention includes a non-transitorycomputer readable medium, comprising instructions for performing themethod of the first embodiment, optionally with one or more of Elements1-18.

Yet another embodiment of the present invention includes a device fordetecting material conditions of at least one hysteretic ferromagneticmaterial and/or at least one nonhysteretic material, wherein the devicecomprises: at least one magnetic transmitter configured to output aninterrogation time varying magnetic field; at least one magnetic sensorand/or acoustic sensor configured to receive a magnetic response and/oracoustic response, and to convert the magnetic response and/or acousticresponse into magnetic response signals and/or acoustic responsesignals; and a processor, configured to execute a method, the methodcomprising detecting the magnetic signals and/or acoustic responsesignals over time from at least one magnetic sensor and/or acousticsensor; determining a time dependent non-linear characteristic of themagnetic signals and/or acoustic signals; and correlating the timedependent nonlinear characteristic of the magnetic signals and/oracoustic signals to one or more material conditions of the material.Optionally, this embodiment can include one or more of the following:Element 1; Element 2; Element 3; Element 4; Element 5; Element 6;Element 7; Element 8; Element 9; Element 10; Element 11; Element 12;Element 13; Element 14; Element 15; Element 16; Element 17; Element 18;Element 19: wherein the device includes an output device configured toindicate to a user the one or more conditions of the material; Element20: Element 19 and wherein the device includes an indicator, whichimplies to notify one or more nearby users for appropriate immediate,real-time actions, and the users can directly observe the indicator;Element 21: Element 19 and wherein the device includes a device forcommunicating to users, which also implies notify users for appropriateimmediate, real-time actions, but the users may be at a remote location,and the communication may through wired or wireless routes; Element 22:Element 19 and wherein the device includes a data collection and storagedevice for later retrieval and post-processing, which is not forimmediate, real-time actions; Element 23: wherein the processes includedetermining and correlating a time dependent non-linear characteristicof the magnetic signals and/or acoustic signals is in real-time with acomputer on board; Element 24: wherein the magnetic signals and/oracoustic signals are stored to a computer readable storage media forpost processing steps including determining and correlating a timedependent non-linear characteristic of the magnetic signals and/oracoustic signals; Element 25: wherein the at least one magnetic sensorand/or acoustic sensor is 4 copies of magnetic sensors and/or acousticsensors at different locations around and/or paired with each of the atleast one magnetic transmitter; and Element 26: wherein the at least onemagnetic sensor and/or acoustic sensor is 8 copies of magnetic sensorsand/or acoustic sensors at different locations around and/or paired witheach of the at least one magnetic transmitter. Example of combinationsinclude, but are not limited to, Elements 1 and 3 in combination andoptionally in further combination with Element 2; two or more ofElements 4-6 in combination; Element 7, Element 8, Element 10(optionally one or both of Elements 11 and 12), Element 13 (optionallywith one or both of Elements 14-15) in combination; Element 16 incombination with one or more of Elements 4-6 and optionally in furthercombination with Element 17; Elements 16 and 17 in combination; Element18 in combination with one or more of Elements 1-17; one or more ofElements 1-18 in combination with one or more of Elements 19-26; Element19 in combination with two or more of Elements 20-22 and optionally oneor both of Elements 23-24; Element 25 and 26 in combination (e.g., twoor more configurations of device implemented together such as in atool); Element 25 and/or Element 26 in combination with one or more ofElements 1-24; and any combination thereof.

While the apparatus and methods of the subject disclosure have beenshown and described with reference to embodiments, those skilled in theart will readily appreciate that changes and/or modifications may bemade thereto without departing from the spirit and scope of the subjectdisclosure.

1. A method for determining material conditions of at least onehysteretic ferromagnetic material and/or at least one nonhystereticmaterial, comprising: interrogating the hysteretic ferromagneticmaterial and/or the nonhysteretic material with an input time varyingmagnetic field; detecting a magnetic response and/or acoustic responseover time from the hysteretic ferromagnetic material and/or thenonhysteretic material; determining a time dependent nonlinearcharacteristic of the received magnetic response and/or acousticresponse; and correlating the time dependent nonlinear characteristic ofthe received magnetic response and/or acoustic response to one or morematerial conditions of the material.
 2. The method of claim 1, whereinthe interrogation magnetic field includes additional magnetic fields. 3.The method of claim 2, wherein the additional magnetic fields includes aconstant DC magnetic field.
 4. The method of claim 1, wherein theinterrogation magnetic field includes a degaussing magnetic field. 5.The method of claim 1, wherein the one or more material conditions ofthe material is a material phase, and wherein the material includes atleast one hysteretic ferromagnetic material.
 6. The method of claim 1,wherein the one or more material conditions of the material is thepresence of a nonhysteretic material, and wherein the material includesat least one hysteretic ferromagnetic material.
 7. The method of claim1, wherein determining the time dependent non-linear characteristicincludes performing a frequency domain analysis that includes powerspectral density analysis of the received magnetic response and/oracoustic response to create power spectral density data.
 8. The methodof claim 7, wherein determining the time dependent non-linearcharacteristic includes determining one or more harmonic peak values ofthe power spectral density data.
 9. The method of claim 8, whereindetermining the one or more harmonic peak values includes determiningone or more harmonic coefficients of the spectral density data.
 10. Themethod of claim 9, wherein determining the one or more harmoniccoefficients and/or peak values includes determining odd harmoniccoefficients and/or peak values of the spectral density data.
 11. Themethod of claim 10, wherein determining the odd harmonic coefficientsand/or peak values includes determining 3rd and/or 5th harmonics of thespectral density data.
 12. The method of claim 11, wherein correlatingthe time dependent nonlinear characteristic includes comparing andcorrelating the 3rd and/or 5th harmonics to the one or more materialconditions.
 13. The method of claim 8, wherein determining the one ormore harmonic coefficients and/or peak values includes determining evenharmonic coefficients and/or peak values of the spectral density data.14. The method of claim 13, wherein determining the even harmoniccoefficients and/or peak values includes determining 2nd harmonics ofthe spectral density data.
 15. The method of claim 14, wherein thewherein correlating the time dependent nonlinear characteristic includescomparing and correlating 2nd harmonics to additional materialsinformation including magnetization state of the materials and thepre-existing residual magnetization of the materials.
 16. The method ofclaim 1 further comprising: wherein the one or more material conditionsof the material are one or more first material conditions of thematerial; repeating the steps of interrogating, detecting, determining,and correlating with the input time varying magnetic field in adifferent configuration to produce one or more material secondconditions of the material; and combining the one or more first materialconditions and one or more material second conditions of the material toproduce combined data set that represents the one or more materialconditions.
 17. A non-transitory computer readable medium, comprisinginstructions for performing a method, the method comprising:interrogating a hysteretic ferromagnetic material and/or a nonhystereticmaterial with an input time varying magnetic field; detecting a magneticresponse and/or acoustic response over time from magnetic sensors and/oracoustic sensors; determining a time dependent non-linear characteristicof the received magnetic response and/or acoustic response; andcorrelating the time dependent nonlinear characteristic of the receivedmagnetic response and/or acoustic response to one or more materialconditions of the material.
 18. The non-transitory computer readablemedium of claim 17, wherein determining the time dependent non-linearcharacteristic includes performing a frequency domain analysis thatincludes power spectral density analysis of the received magneticresponse and/or acoustic response to create frequency domain data thatincludes power spectral density data.
 19. A device for detectingmaterial conditions of at least one hysteretic ferromagnetic materialand/or at least one nonhysteretic material, comprising: at least onemagnetic transmitter configured to output an interrogation time varyingmagnetic field; at least one magnetic sensor and/or acoustic sensorconfigured to receive a magnetic response and/or acoustic response, andto convert the magnetic response and/or acoustic response into magneticresponse signals and/or acoustic response signals; and a processor,configured to execute a method, the method comprising detecting themagnetic signals and/or acoustic response signals over time from atleast one magnetic sensor and/or acoustic sensor; determining a timedependent non-linear characteristic of the magnetic signals and/oracoustic signals; and correlating the time dependent nonlinearcharacteristic of the magnetic signals and/or acoustic signals to one ormore material conditions of the material.
 20. The device of claim 19,wherein the interrogation magnetic field includes additional magneticfields.
 21. The device of claim 20, wherein the additional magneticfields include a constant DC magnetic field.
 22. The device of claim 19,wherein the device includes an output device configured to indicate to auser the one or more conditions of the material.
 23. The device of claim19, wherein the at least one magnetic sensor and/or acoustic sensor is 4copies of magnetic sensors and/or acoustic sensors at differentlocations around and/or paired with each of the at least one magnetictransmitter.
 24. The device of claim 19, wherein the at least onemagnetic sensor and/or acoustic sensor is 8 copies of magnetic sensorsand/or acoustic sensors at different locations around and/or paired witheach of the at least one magnetic transmitter.